I has desktop. It is some crappy Acer Aspire (w/ Athlon processor), which has XP and was only loaded with 256MB of RAM in one of the two slots.

It was freezing repeatedly. Simply not giving any response whatsoever. Eventually someone sends me a couple of new bits of RAM, I shove one of them (a similar 256MB stick, albeit this one is branded) in, everything works fine.

Now I get tired of Firefox being such a huge memory hog and taking forever to load, so I order 1GB worth of Kingston RAM. I install the thing, in place of the single piece of RAM that was in there originally. It only shows 960MB in Windows, but it's recognised and FF is sped up, so it's all kosher.

Then it hangs, and comes up with an error. It doesn't crash it, but I can normally reboot so I think it's just some random error. I reboot, and load up FTP and try to 4-table. It freezes. I assume it's FTP and reboot. I load up a couple of heads up SNG's. I win one, and then it freezes. I reboot, stack the German douchenipple that stole all my blinds while I sat out, then assume it's the FTP client. After a while, my computer locks up again.

I reboot, do not touch FTP at all, looks to be OK, go out to the pub. Come back, as I have multiple users on this PC I try to log back in. I can log back in, but do nothing else at all, it's as if everything is frozen.

I have run memtest86 and the memory seems OK, I have run prime95 on my machine continually since getting the other bit of RAM that's been in there since the first upgrade, and that seems stable.

I don't have a clue where the problems are coming from. Everything is recognising the new RAM, and it seems to be OK, but it just breaks. I'd like to rule out other hardware problems seeing how I've run the machine for at least three years without problems. WTF?

I assume you didn't mix the ram...

Also, if you put the old RAM in, is everything back to normal?

also try moving the ram to a different slot.

i'm getting POST beep codes now... going to try swapping the slots, then just having the 1GB stick in on its own before reverting to the old setup and getting the thing working at all

[edit - then i try booting it again and it works, odd]