|In response to your PM to me...|
What it all boils down to is you bought a 1gb ram module that is NOT COMPATIBLE with being used in your mboard. If you bought it locally, take it back and get a refund.
If you bought it on the web, ship it back and get a refund.
However, you may not actually get a refund until the ram has been tested and found to be okay, and a fee may be deducted from the refund because you returned it and it wasn't their fault you bought the wrong one (re-stocking charge, etc.) . Shipping charges are not refundable, unless the seller specified the module you bought would definately work in your mboard.
You quote both 502 and 504mb as being the total amount or ram reported in Windows. I'm assuming 502mb is a typo, or you were quoting the wrong amount.
If you're quoting the right amount..
E.g. if you RIGHT click on My Computer - Properties - the total amount of ram reported by the mboard's bios is shown on the right on the first screen you see
.... then it was probably 504mb.
When you are using video built into the mboard - onboard video - some mboard bioses subtract the amount of ram that is being shared with the onboard video because it can't be used by the operating system for other uses, and if so, Windows reports that same amount.
In your case, the mboard's bios is subtracting 8mb at present.
Onboard video always uses/shares ram in certain even multiples, 2 to the x power, except for the first choice - e.g. 8, 16 (8 x 2; 2 to the first power) , 32 (8 x 4; 2 squared), 64 (8 x 8; 2 cubed) , 128 (8 x 16; 2 to the 4th power) , 256 (8 x 32; 2 to the fifth power), 512 (8 x 64; 2 to the sixth power), etc. mb
"I replaced one of the 256mb rams with the 1gb ram still my pc showed 502 mb of ram and I even tryed to leave the 1gb ram in the pc alone with out a 2nd ram it still showed 502 mb"
I'm assuming both 502s in that are supposed to be 504.
Onboard video can't use 10mb.
The 256mb module is probably not being detected at all when the 1gb is installed along with it. The 1gb module is being detected as 512mb, half of it's true size, minus 8mb for the amount of ram shared with the onboard video.
"Do any of u think me reinstalling windows can fix this ?"
Windows has nothing to do with your problem.
The total amount of ram reported in Windows is determined by the mboard's bios.
When you're using onboard video, the bios may or may not subtract the amount of ram being shared with that onboard video from the total amount of ram dtected by the bios.
The amount of ram detected by the bios is correct only when you use ram modules that are all 100% compatible with being used in your mboard - in this case, compatible with what the memory controller in the main chipset on your mboard requires.
Gledsters info in Response 1 does not apply to your mboard.
You DO NOT randomly buy ram.
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 all the way with it installed, and the mboard may not even beep - the ram has to be compatible with the mboard's main chipset, or in the case of recent mboards, compatible with the memory controller built into the cpu.
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:
Correction to that:
Once you know which module ID strings (part numbers) 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 (part number) 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.
"I suspect you have bought RAM with too high density chips on it.
According to crucial.com your board can accept up to 1GB of RAM in each slot. However, if 1GB it must have 8 128MB chips on it. Not 4 256MB chips on it."
"Count the chips on the RAM stick to see how many there are. "
That may be what your problem is.
"I have 2 slots... "
"Dell Optiplex Gx280 SFF"
However, depending on where I look, 1gb or 2gb modules are specified as the max size you can install in your Gx280 small form factor series mboard, which has two ram slots.
(There is a mboard for the Gx280 minitower / desktop series that has 4 ram slots - that's NOT your mboard.)
Usually when various sources disagree about the max module size, the ones that state you can use larger modules have updated info and that info is correct.
E.g. for the Gx280 SFF (Small Form Factor) series...
Kingston specifies a 2gb max module size.
Model: Gx280 small form factor
Click on search
Crucial specfies a 1gb max module size.
Corsair specifies a 2gb max module size.
Memory Giant specifies a 1gb max module size.
"Also, your board utilizes dual channel memory controllers.
What that means is you will get better performance from two identical sticks of 512MB instead of one stick of 1GB."
Your mboard can use either single channel ram, or dual channel ram, which is sold in matched pairs of identical modules of the same capacity, or, pairs of indentical single channel ram modules of the same capacity (size) can run in dual channel mode.
When your mboard has more than two ram slots, in order for all of it to run in dual channel mode, all the ram must be compatible with running in dual channel mode - each pair has to be in certain slots, each pair has to have identical sized modules but the pairs don't have to be using the same sizes of modules.
However, in the real world, having all your ram running in dual channel mode yields only a tiny improvement in performance of the ram - a few percent at best.