About two weeks ago I bought 2 x 1gb of RAM to replace the 2 x 256mb and 1 x 512mb RAM in my PC.
AT first everything was ok then programs stopped working BSOD’s started appearing and I had terrible trouble trying to boot the PC even in safe mode. Windows started telling me I need to activate it within three days.
Suspecting duff RAM I tried using each of the 2 new cards separately and together in all of the three different slots but the problems persisted so I sent it back and replaced the old RAM.
Everything was ok for about a day then the same trouble started again but in addition when I eventually got it booted (not easy) it registered only 512mb RAM but it had a total of 1024mb.
Checking the system with Belarc showed a total of 512mb but also showed that slot 1 had 256mb, slot 2 had 256mb and slot 3 had 512mb!
I have tried the cards separately and together in different slots but it didn’t help. Sometimes I restart the PC and find it is registering 1024mb. I still keep getting requests from Windows to activate it despite doing every couple of days.
I have also restored an older version of my system with Acronis TI, which made no difference, so it doesn’t appear to be a software problem.
All AV and antispyware is up to date and showing no issues.
Finally, the memory I returned WAS found to be defective.
I hate to suggest this, but it's sounding as if the defective ram has in some way buggered up the memory slots or the mobo. (and that may in turn have affected the old ram since it went back in)
You could try downloading Memtest86, creating a bootable disk, and start the pc with it in the drive. However, if it does report memory failures as I suspect it might, you still won't know if it's the board or the ram.
I have ruled out the PSU as a problem by trying an old one.
I certainly intend to try switch cleaner when I can get to Maplins and I will also try resetting the BIOS but not until my new (Vista) PC arrives as this is the only contact with the internet that I have at the moment and have never tried messing with the BIOS before.
The new memory was identical in every respect (apart from size) to the old memory.
Something I didn't mention earlier is that the PC is most likely to register the full RAM if it is left on for several hours before resetting. Suggesting that it might work better when warm?