Specs: Windows XP SP2, 3.4 gHz Intel 4, plenty of HD space (2 HDs).

I'm not sure what is going on but about two months ago my computer stared to slow down significantly. At first I thought it was just a program I was running (Sibelius 4) but then I noticed it happening with other programs too. Here's what's going on. If I start up my computer it runs great for a few minutes or so but then suddenly it's like my CPU starts to work really hard and everything slows down. I've been through everything (spyware, viruses, extra programs I don't need, I've defraged, cleaned my registry, changed all my settings so windows will run as fast as possible etc). Nothing seems to work so my question is, could this be a hardware issue? Oh, another thing I definately should mention. When my computer slows down a simple restart doesn't solve the problem. I actually have to turn the machine all the way off (including the surge protector) to get it to run fast again. Anyone have a clue what could be going on? I'm lost here,

Oh, another thing that may or may not be related but I'll ask anyway. Sometimes if my computer freezes and I have to manually restart it my settings are changed (as in windows in all pretty again, I have it set for best performance). Does anyone know why this might be happening? Anything would help.

Sorry this is so long...

Nick

PS I know ONE of my problems is that I'm running windows...