This machine has two 256M slots with a system max of 512M. I took a chance and installed a spare 512M chip I salvaged from another dead pc. I was curious if 256 slot would read 1/2 the card. I have read of this happening to others. Seemed like a good idea at the time. The chip could not be read by the PC, but worse than that, when I removed it the PC would not boot, giving the message that a Windows file had been corrupted. I'm not asking for help... I know what has to be done (I can hear many of you suggesting "just toss that boat anchor - haha). But I'm curious if anyone has heard of over-stuffing a memory slot like this causing damage to the operating system. Another option is that the 512 chip had a bad failure. The operating system on the hard drive removed from the same dead PC I took the chip from coincidentally had similar symptoms (trashed OS). Is it possible for a failed chip to scramble the OS?

Did the PC boot up with the suspect chip installed and simply not show it in "My Computer" properties? If so then it may be responsible for your file corruption problem. If I were doing the experiment I would have disconnected the harddrive and simply booted up into bios to see if the ram were recognized. If you decide to go down this path try booting with a Memtest86 bootfloppy. It may or may not be able to test the 512mb stick. Depends on what is shown in bios. I have an old Compaq Deskpro system that the manual says can take a maximum 128mb in each slot for a total of 256mb. Has a sticker on it that says "Designed for Windows NT/98" I experimented with it and discovered that it will accept sticks of 256mb Double-sided low density SDRAM. That system has a 500Mhz processor and runs XP quite well with 512mb ram. Goin' Fishin' (Some day)

"The operating system on the hard drive removed from the same dead PC I took the chip from coincidentally had similar symptoms (trashed OS)" Did you take a HD, with XP on it, from 1 PC & try to put it in another PC?? larry

"The chip could not be read by the PC, but worse than that, when I removed it the PC would not boot, giving the message that a Windows file had been corrupted." Did you remove the AC power to the PS while fiddling with the ram, or anything else connected to the mboard inside the case, at all times?? If you didn't, ATX mboards are always powered in some places even when the computer is not running, as long as the PS is getting live AC, and it's switch is on if it has one, and you can damage things by simply plugging in or unplugging them. What was wrong with the dead PC? Did the PS fail? That can damage the ram, but usually it doesn't. If the PS didn't fail, if ram was not comptible with that mboard either, it could be that's why it would not boot, and could explain the data damage. Ram that works in another mboard , or any ram you buy or have lying around, may not work properly, or sometimes, not at all - even if it physically fits and is the right overall type (e.g. SDram, DDR, DDR2, etc.; PCxxxx, xxx mhz) for your mboard. In the worst cases of incompatibilty your mboard WILL NOT BOOT with it installed, and the mboard may not even beep - the ram has to be compatible with the mboard and it's chipset. See response 5 in this for some info about ram compatibilty, and some places where you can find out what will work in your mboard for sure: http://www.computing.net/hardware/w... Correction to that: Mushkin www.mushkin.com Once you know which module ID strings work in your mboard, you can get them from anywhere you like that has ram with those ID strings. If you have brand name ram, it is usually easy to look up whether it's ID string is in a list of compatible modules found by using your mboard or brand name system model number. If the ram is generic, that may be difficult or impossible. ...... " have an old Compaq Deskpro system that the manual says can take a maximum 128mb in each slot for a total of 256mb. Has a sticker on it that says "Designed for Windows NT/98" I experimented with it and discovered that it will accept sticks of 256mb Double-sided low density SDRAM." Does it have a Via MVP3 chipset? Some older mboards were originally specified to support no more than 128mb in each DIMM slot, in their specs and in their manuals, but in reality they DO support twice that in each slot if they have certain chipsets. E.g. mboards with the Via MVP3 series often said they only supported 128mb max in each SDram slot, but in fact they DO support certain 256mb modules with lower density chips (16 chips, 8 on each side) in each slot. The memory module manufacturers and major ram distributors have the correct info when you look up which modules work in that mboard model on their web sites, and they have had since not long after those mboards were made. Via MVP3 chipsets support up to 768mb of ram, total. So do MVP4 chipsets, but by the time MVP4 chipsets came out, most specs and manuals had the correct info for them - they support 16 chip 256mb modules in each slot too. However, on those mboards, how much of that ram is cached depends on the size of the L2 cache on the mboards they are on. E.g. A 1mb L2 cache supports caching up to 512mb of ram. If you install more ram than the L2 can handle, NONE of the ram is cached, resulting in about a 25% performance hit on those mboards. Lots of them had only a 128kb or 256kb or 512kb L2 - some el-cheapo ones had no L2 installed at all. "That system has a 500Mhz processor and runs XP quite well with 512mb ram." If it has a MVP3 or MVP4 chipset - what size is the L2 on the mboard? - your mboard will run a K6-2+ 550 cpu (lower core voltage, made for laptops) at 600mhz if you use the X2 multiplier setting (K6-2's interpret X2 as X6) and you can select it's voltage, without overheating with a stock heatsink and fan. ..... Yes, installing incompatible ram can sometimes cause damage to your data on the hard drive. Usually you can tell whether it's incompatible by running a memory diagnostic on it BEFORE you attempt to boot a hard drive, IF the computer boots normally with it in, but sometimes even that isn't enough. If you're not sure, disconnect the hard drive, and test the ram first! I had a case recently where I had a 256mb PC133 SDRam module installed in a mboard, and I added a PC133 128mb module, and tested the ram using a memory diagnostics program - it passed. I then attempted to boot an existing Windows installation and got errors which I had not gotten before - breif display then it black screened and rebooted, not enough time to rerad the message. Since the hard drive may have needed to have a "Repair install" run on it, since I had changed the mboard, I then tried running a "Repair install" from a Windows XP CD, but got lots of errors loading files from the Windows CD, so I quit Setup. I took out the 128mb module, changed the CD IDE data cable, ran Setup again, got no errors loading files from it, but because I had quit Setup, the second Repair option was no longer there, so I had to run a regular Setup. Later on I needed to reload Windows again, and tried installing both of the same modules again, thinking the problem had been the data cable. Same thing - lots of errors trying to load files from the CD - take out the 128mb module - no errors. I ran some tests with the 256mb module along with several 128mb modules one by one, and pairs of 128mb modules - when that 256mb was installed, it would produce errors reading the files from the CD when any of the 128mb were installed at the same time, some pairs would pass all memory tests when both were installed, some would not. All the 128mb modules produced no problems individually or in combo with another 128mb one. The 256mb one tests fine when by itself, and no errors reading files from the CD. I strongly suspect my installing that 256mb module and 128mb module in the first place trashed at least some of the data already on the hard drive - I didn't even get the usual symptom you get when XP needs to have a Repair install run when you have changed mboards - the first bit of Windows graphics, then a black screen, blinking cursor top, nothing further happens. ........ It is easy to test for incompatible ram that has caused your mboard to fail to boot. Make sure you have a speaker or speakers connected to the mboard so you can hear mboard beeps (see your mboard manual). Remove the AC power to the case/power supply. Remove all the ram. Restore AC power. Try to boot. If nothing else is wrong, you will hear a pattern of beeps that indicate no ram is installed, or a ram problem. E.g. for an Award bios or a bios based on one, that's often a beep of about a half second, silence for a half second, a beep of about a half second, silence for a half second, continuously.

Hi All, and thanks for the replies... Richard: I neglected to mention that the PC simply does not boot with the 512 chip installed. It freezes up almost immediately after power up. Good suggestion to disconnect the hard drive before experimenting. I'll remember to do that in the future. The PC I endangered has one 128 and one 256 chip, and does a decent job of running XP. It's a bit slow of course, and I can't have more than a couple of apps open at once. I was hoping to bump it up to 512 as I figure that would boost the performance a little. Larry: Yes, the hard drive I removed from the dead PC has XP on it and was installed into yet a 3rd pc. It wouldn't boot at first, but after an XP Repair it booted fine and all the original desktop settings and programs are still intact. Of course, I did have about a gazillion Windows updates to wade through, because my XP disk is old (pre SP2). Tubesandwires: Holly cow, thanks for all the detail! I reckon it's a safe bet you've had your hands in more than a few PCs. I did not disconnect the AC. I've installed many components over the years without doing so without any trouble, but I now appreciate that I've been very lucky. It just takes one incident like this to realize you want avoid causing something like this through your own poor practices. On the PC that died, its first symptom was it starting shutting itself off from time to time. Eventually it just refused to boot up any more. I removed all the PCI/AGP cards, disconnected all the drives, reseated the CPU, and tried removing the RAM modules one at a time (both of which had worked fine together for a long time) and it still would not boot, so I figure there must a problem with the motherboard. "In the worst cases of incompatibilty your mboard WILL NOT BOOT with it installed, and the mboard may not even beep" - yes, no beeping is the case when the 512 module is installed along side the original 256, and the PC simply freezes when turned on. When the 512 is installed alone, the PC does go through a beep sequence. "I didn't even get the usual symptom you get when XP needs to have a Repair install run when you have changed mboards" - ah, so it isn't unusual to have to run the XP Repair when mating an existing OS to a different motherboard. I don't remember having this problem with earlier versions of Windows, is this a particular quirk of XP? Back to the PC with the memory experiment. I thought I had a damaged XP OS because with the original RAM installed, the PC failed to boot and displayed a message stating than a system file was corrupt and suggesting I might be able to use XP Repair to restore it. I don't remember the name of the file, but I do remember it had something to do with PCI. However, at the time I first installed the 512 module, I had also installed a network adapter card (also from the dead pc). I know, I know... another major no-no... two changes at once. I discovered that the network adapter was not fully seated. After rectifying that issue, the PC began booting and no longer presented the corrupt file message. Somehow XP had been *fooled* into detecting there was a bad file. But then I started getting an "ERROR Resource Conflict - PCI in Slot 02" message (where the network card was). I finally cleared up the problem by removing all the PCI cards and booting up with just the network adapter card installed first. Then I was able to re-install the other cards and all is now normal. What FUN! And yes, I did try the 512 module yet one more time after fixing the network adapter issue, but got the same negative results. Thanks again to all for contributing to this discussion... it was very enlightening.

I'm glad to hear you solved your problems! "I did not disconnect the AC." Usually things are not damaged anyway, but why take a chance. E.g. ram slots and video slots are certainly powered at some contacts all the time. You can easily fry an AGP video card if you plug it in or unplug it because of the two levels of staggered contact positions on the card and in the slot. I almost always do this, but didn't one time when I merely plugged in a hard drive and got a tiny spark while doing that - doing that fried the PS, probably it's control circuit. Most older AT moards are completely unpowered when you turn off the power switch because it's directly connected the the AT PS and switches off the AC to the PS. "On the PC that died, its first symptom was it starting shutting itself off from time to time." The most common reasons for that - the PS is failing - the cpu has overheated - the cpu fan is no longer spinning fast enough or is not spinning (the bearings are failing), and/or the cpu heatsink is clogged with mung. On older mboards if that goes on too long, there may no built in bios related temp protection and the cpu fries. Rarely, mostly seen with older mboards....your mboard may have faulty electrolytic capacitors. This has happened to me once, and twice on mboards of other people I know. Usually there's nothing wrong with the ram or the cards, or the cpu, unless it overheated. Contrary to popular belief, it is extremely rare for ram that worked fine previously to go bad, and even then the odds against of more than one going bad at a time are nearly impossible. I've never encountered a mboard that needed the cpu to be reseated when it worked previously, at least not one in a ZIF socket - they are extremely reliable. Open up your case and examine the mboard to see if you have bad capacitors, and/or other findable signs of mboard damage . This was the original bad capacitor problem - has some example pictures. History of why the exploding capacitors and which mboard makers were affected: http://members.datafast.net.au/~dft... What to look for, mboard symptoms, example pictures: http://www.badcaps.net/pages.php?vid=5 Home page that site - what the problem is caused by - he says there are STILL bad capacitors on more recent mboards. http://www.badcaps.net/ Pictures of blown capacitors, other components, power supplies, Athlon cpu's, etc.: http://www.halfdone.com/Personal/Jo... "...ah, so it isn't unusual to have to run the XP Repair when mating an existing OS to a different motherboard. I don't remember having this problem with earlier versions of Windows, is this a particular quirk of XP?" 2000 does the same. It depends on how different the main chipset is, mostly. If they are similar enough, 2000 or XP does the same thing 95, 98, 98SE, and ME did. Usually 98SE, 98, or 95, will merely detect the components are different and load stuff for that while booting, but I've had to run a "overtop" Setup in 98SE a few times. I haven't used ME much. ""ERROR Resource Conflict - PCI in Slot 02" message" If you are still able to boot, you may be able to determine what the problem is in System Information or Device Manager. Don't use the PCI slot on the end closest to the middle of the mboard for anything except a PCI video card - that slot is usually forced to share it's IRQ with the onboard video or the video slot and that often causes problems. If you have more than 3 PCI slots, some of the higher numbered slots may share that same IRQ - the mboard manual often has that latter info. Sometimes this fixes the problem: - shuffling which card is in which slot. A card in a lower numbered slot usually has lower IRQs available. - setting the PNP aware OS or similar setting in the bios Setup to enabled or yes if it is disabled or no, or visa versa. - free up IRQs for devices you aren't using - if you disable PS/2 mouse support in the bios, that often frees up IRQ 12, which some network cards or USB controllers can use. - you may be able to shift which IRQ or IRQS USB uses by disabling the USB controllers in the bios Setup, save settings, reboot into Windows at least once, boot again, enable the USB controllers in the bios Setup.

"Don't use the PCI slot on the end closest to the middle of the mboard for anything except a PCI video card..." Coincidentally, I had moved the network card to slot 1 to see if maybe slot 3 was just bad. The video card ended up in slot three (closest to the middle). Sometimes you just get lucky. I just trashed the dead MB, and salvaged all the parts for other PCs. Which brings up another question about odd CDR behavior... but that'll be another post. If I get home before the trash truck comes I'm gonna pull out the MB and look for signs obvious damage. thanks again.