I thought this was best posted here since I don't know if it's a hardware or software problem...
Let me explain. When my PC has just been turned on, it runs fine - just as you expect it would. It does this until I've finished playing a game (or occasionally when I'm ~30 mins into playing a game), then it decides to slow down, and I mean noticably. If I'm playing a game at the time, I loose ~20 FPS. It's like it's decided to start loading stuff off the hard drive, except it isn't.
The same thing happens if I'm not playing a game, it just seems to take longer (after having been on for about 40 mins). Everything I do takes longer - every time I load something, it hangs.
When I mentioned the game part of it to a mate he said it might be because I've only got 512MB RAM (he had the same (almost) problem with games hanging mid-play when he'd just bought a 6800GT). He upgraded pretty sharpish to 1GB and found it really helped.
So I've ordered another 512mb stick, should be here on friday. I just hope it's the problem - TBH the fact that my pc just slows down for the rest of the time it's on doesn't sound like a lack of RAM problem... does it?