Why my computer is not showing the ram

[Attiq]

Hello,
my computer's ram is 512mb+512mb but it shows 256 I removed them one by one and found same status.... plz help....

 

[Hawkeye22]

Is that what windows is showing? If so, go into the bios and see what it's reporting for ram or if you can view your post screen, what is the post screen showing for your memory count? If the bios is only reporting 256, then windows will only see 256.

Also, be sure you actually are using 2 x 512 Meg sticks. In order to run in dual channel, you need sticks that match in specs.