I've been running an MSI KT6 MOB with an Athlon 2500 processor for several years. I had one gig of memory which wasn't enough for some of my photo programs so I decided to add a gig of memory.
At the local Circuit City I say some i gig ram (don't have the infor with me) but was bas backward compatible to my 400 speed bus. It appeared to have the same pin setup as mine except it was DDR2 and my original was DDR PC3200. The nerd assurred me it should work.
So I took the two memory sticks home, took out the old one and put the two new ones in. They fit the slots but wre harder to insert than the old ram. Turned on the computer--absolutely nothing. Not even an attempt to boot.
My big mistake probably was pulling one of the new sticks and insert my old memory along with a new memory stock. That didn't work either and after I removed all the new memory, the old doesn't work either. No attempt to boot. The cd drive lights wink, the hard disk access light come on a glows steady gree, and nothing else happens.

My question: Can the wrong memory physically damage a MOB or processor or existing memory? I would like to think replascing the old memory with a new correct stick would get things up and running again. But I hate to buy another stick of the right ram and then discover it won't work.

Meanwhile I bought a laptop but it uses the Vista OS and I need to get the old computer running because the new one won't run my Canon scanner.

Two things you may have done wrong. First, not unplugging the computer. Second, not looking at the notches in the bottom of the module. They only go in one way.

All the versions of your KT6 mboard use only DDR ram.

Some mboards have both DDR ram slots and DDR2 ram slots - you use one type or the other of ram, not both, and each type must be installed in the proper slots - but that does NOT apply to your mboard.
It cannot use DDR2 ram.

"They fit the slots but wre harder to insert than the old ram."

The modules are the same physical length, but amongst other things, the notch in the contact edge of the module is in a different place. DDR2 cannot be installed so that it sits flat on the bottom of a DDR ram slot, and visa versa. DDR2 ram uses a much lower voltage than DDR ram does. DDR2 ram has more contacts than DDR ram does.

The differences:
http://www.kingston.com/newtech/ddr...

......

If you typing DDR2 was a typo on your part, and you actually got DDR ram,
"They fit the slots but wre harder to insert than the old ram."

They should go in just as easily as the old ram, if the notches in the contact edge are lined up properly with the bumps in the bottom of the slots. If you inserted them backwards, it is difficult if not impossible to get the latches at both ends of the slot to latch into the end of the module because the module cannot go all the way down in it's slot where the notches don't line up with the bumps - you are forcing the bottom of the slot to bend. If any module was backwards when you attempted to boot the computer, any ram module that is in backwards is fried instantly, and the slot that backward ram module was in is instantly ruined and can never be used again. Hence, the old ram modules will not work in the ram slots that were damaged.

Take a look at the contacts on the new modules - if any contacts are missing and/or there are obvious carbon deposits on the contact edge, they have been zapped by installing them backwards.
Similarly, using good lighting and possibly a magnifying glass, examine the ram slots - if you see any contacts are missing and/or carbon deposits and/or melted plastic in the slots, that slot is fried and can never be used again.
If you do see damaged ram slots, you could try cleaning out all carbon deposits and melted plastic in the damaged ram slots such that no plastic bridges two contacts, and no contacts are fused to each other, then
- if you are fortunate, undamaged ram MAY work fine in any remaining undamaged ram slots
- if you are NOT fortunate, the mboard will never work again no matter what you do.
.....

Installing DDR ram in your mboard that is incompatible with the mboard chipset can cause the mboard to not boot, but it won't hurt the mboard if it is installed such that the notch lines up with the bump in the slot.

Using DDR ram of a higher PCxxxx rating than the mboard was rated to use may or may not work but it also won't hurt the mboard if it doesn't work if it is installed such that the notch lines up with the bump in the slot. The problem with using a higher PCxxxx rating than the mboard was rated to use is there is nowhere where you can look up whether it will work for sure - is compatible - the PCxxxx rating itself is backwards compatible, but that's not the only thing that determines ram compatibility.

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

Regardless of what the "nerd" told you, you are ultimately responsible for checking things out. Even if you didn't know beforehand that DDR & DDR2 have a different pin count & different notches along the contact edge, you could have (& should have) compared the old RAM to the new before forcing them into the slots. A quick visual comparison would have told that it wouldn't fit. The voltages are totally different too.

You quite possibly fried the whole system...you won't know until you troubleshoot. The fact that your system will no longer boot with the old RAM is not a good sign. You most likely fried the board & probably fried the new RAM too.

BTW, the AXP 2500+ runs at 333MHz FSB, not 400MHz. If you weren't overclocking, all you required was DRR333 (PC2700) or DDR400 (PC3200) clocked down to DDR333 speed. Running DDR400 @ 400MHz with an AXP @ 333MHz degrades performance.

The DDR2 ram notch was just a fraction of an inch off--that sould have tipped me off. Anyway, since that new ram is lower voltage it definately is fried.

I do have another KT6 board--one with three memory slots rather than two that I can swap out. If the processor is gone it's not a huge deal because it was getting long of tooth anyhow. But it was a solid running XP Pro platform.

It's nobody's fault but mine. The DDR2 ram was a lot cheaper that the 333 DDR memory I should have got and the pins and slots looked "about" right.

Thanks for the info

He couldn't have been that much of a nerd if the dipsh!t didn't know the diff between DDR1 and DDR2. You don't even have to be a computer geek for that matter to know the diff.