Stuttering problems on my laptop.

This is getting really annoying at times, especially while playing games. Frame rate drops dramatically and i'm not talking about some modern titles, rather PSX emulation etc. After few seconds it gets back to normal just to occur again after 20-40 seconds. It's the same with movies, youtube etc. On low resolution movies it's ok, 640x480 works fine by itself, the problems occurs when i switch on the subtitles for example. 720p movies are now impossible to watch, even though i had no problems with them ealier (just like in the games, it only lasts few seconds and after that the out of synch effect dissapears for some time), on youtube is the other way around, video stutters for few seconds but sound is ok. I'm sick of those hickups.

I guess it can be related to hardware in a way. I had to format a month ago but it didn't solve the problem, I'm not using anything terribly memory consuming. Avast, Sygate Firewall, skype, ati drivers and thats about it.

I'm on a Acer 5100 laptop with AMD Turion 64 procesor, WinXP, 1GB of ram and ATI Radeon Xpress 1100.

Jam it back in, in the dark.