some times whene i install a new ram on a mother bord . after restart windows can not show real ram memory !
for example i install a 526 mg ram with a 256 one on a mother board but windows only show 526 and it seems 256 ram is not working !
what is the problem?
is it realy dose not work or this win problem ?!

I believe you mean 512Mb by saying 526 mg, right? =)
You should check if this new RAM memory you got is compliant with you system motherboard clock. Roughly, this means that for safety your system won't accept memories with different speeds from the original and/or memories with different speeds. This can be sometimes bypassed using some advanced BIOS settings or software, but is often very risky. Do you have any idea of your motherboard/processor and both memories BUS speed? Usually there are plenty programs on Internet that give you full logs about your current system specs. On the other hand you can look this by yourself or ask someone with good computer knowledge.
Also, you always can have some dirt on the connectors, or a non-working RAM memory.

yes
i mean 512
but how can i determine system motherboard clock ?
is there any software to do this?
thank you very much

For sure. Here are some I personally like:

Everest Ultimate (The best, in my opinion)

HWInfo32 (Good one as well, lighter)

Sandra (The best versions are for buying =\)

It's up to you choosing, good luck.

There are such incidents. However, you must MAKE SURE THAT YOU INSTALLED IT PROPERLY.

xboxrulz

ok.. so i chked my motherboard... and i have to say tht i found it compliant.. i mean.. my MB supports a 400MHz DDR RAM...

but my 512 MB ram shows up as 480. wat's the prob.. can someone help me please?

The onboard graphics card which is utilized if you don't have a dedicated graphics card installed, is sharing the rest of the 32 MB memory with your RAM. You can lower this amount by going to the BIOS > Video Configuration. Caution: You should not set it to the extremely low values (0, 1 or 8 MB) unless you have and additional graphics card. Your system might not be able to boot in that case. You'll have to reset the BIOS in that case which in turn can be done by the appropriate jumper on your motherboard (check the Motherboard's manual for more detail) or by taking the BIOS battery out.

True, but from the sound of it I doubt he's got a motherboard with 256MB memory option.

What motherboard do you have ? Does it support more than 512Mb RAM (it's probably like 10 years old if it doesn't do so ) ? How many memory modules are already installed ? Are the memory modules single-sided our double-sided (are there memory chips on both sides of the RAM cards ? ) ? Have you tried installing only the 256Mb RAM card ?

like many others here, I too believe that the problem is most likely with hardware compatibility of some type here...

First off, most motherboards only support a certain amount of RAM (for a total), so once you hit that, you can't go over it. For instance, many are at either 512MB, 1GB, 2GB, etc.

Another thing is that sometimes motherboards don't like it if you don't install like chips of RAM (even if they are rated for the same clock speeds and everything), they want you to put in two chips that are the same size....I have run into this several times (although it was usually only a problem with SIMM memory, some of the newer computers seem to complain as well). One thing I would try, is taking out the 512MB chip, and only putting in the other one. That way you can see if the other chip works, and if it does work then, then you probably have either two chips that wont work together, or you have hit your maximum amount of RAM.

If your computer is by a manufacturer such as dell, hp, compaq, gateway. I would suggest looking at the support documentation for the computer, as you should be able to find something there, and if you can't give them a call or an e-mail. Compaq a couple months ago gave me support on my 14 year old computer, giving me information about RAM and stuff, so I would head over to support to find out the types of RAM that'll work, the maximum amount you can have, etc.