I've seen similar problems, but this seems slightly unique, maybe...
I have a Gateway LT21 netbook, Win7.
I've upgraded RAM from 1gb to 2gb.
It didn't work.
So I updated to the latest Bios 1.25, then it worked. 2gb was recognized in the Bios and in Windows.
Every was fine.
Now today it seemed slow and, to my surprise, both the Bios and Win show only 1gb. :/
I've run memory diagnostic, no error.
I entered bios and hit Exit and Save. Still 1gb.
I took out the ram, put it back. Still 1gb. :/
CPU-Z shows 2048mb/2gb of RAM.
Further testing: if i put in the old 1gb ram, turn on, then put in the new 2gb ram again, the Bios and Win show 2gb of ram. BUT, once restarted at all (even from Bios) it seems to go back to showing incorrect 1gb ram again. :// (There are very few options in the bios, none appear memory-related.)