Computer freezing after videos

Well, the computer doesn't "freeze" but it's incredibly slow... like if I move the mouse it will respond about 30 seconds later. I also can't minimize or anything, because it's just way too slow, if I manage to minimize, it's still the same... so what I have to do is, ctrl+alt+del and end firefox.exe.. or if it's not responding, sometimes I'm forced to shutdown manually..

I have tried watching videos, any format, with Winamp, WMP, Realplayer, and Quicktime, all freeze. But I can watch videos from http://www.youtube.com/ for some reason..

Any ideas guys? As this is really annoying some times

 

no, not at all. It only happens when I try to watch videos. Any other times, its fine

 

I have 768mb, and I just reboot my computer, so nothing has been open.
Also, this even happened, right after I reformat my computer. I am using XP Pro with SP2, before I was using Home and had no problems like this..

 

How can I find that out?

 

Never mind, I got it. I just needed to update my video card drivers :/
I always do, just forgot this time when I reformat...