BleepingComputer.com: PC stuttering

Hi, I'm not sure if this is the right place to post it but here goes:

My pc stutters every 10-15 seconds for 10-15 seconds, this however only occurs when I play games both online and offline. It occurs in little crappy games like Bejeweled Twist aswell as in bigger games like Mafia(haven't bothered to install any other games since this is really annoying) it also stutters when I play any game from www.kongregate.com / www.newgrounds.com / or any other website with flash games.
However, and this is partially why I'm stumped, it doesn't stutter when I play music or watch movies and when I stream music or movies.
Sometimes it will even stutter when using youtube.com, I have however not found any consistency with youtube, seems random.
Also I've tried having taskmanager open to see if any processes suddenly spike with cpu usage but there doesn't even seem to be a pattern there, sometimes the game will increase cpu usage during stutters other times it'll be firefox or a third program.
I've tried moving the pagefile to storage hdd.
I've tried shutting off PhysX from Nvidia controlpanel
And plenty of other stuff but nothing works for me.

Anyone able to help me?

My specs are:
Maxtor 6Y160L0 150gb ide hdd <-- Windows xp sp3
Samsung HD103UJ 1tb sata hdd <-- Storage
Lite-on DVD D LH-16D1P
AMD Athlon 64 X2 Dual Core Processor 6000+
Nvidia GeForce GTX 275
4 gb RAM

Does the computer stutter when doing heavy multitasking? If so, it might be overheating. AMD's have a habit of being a little on the hot side. Try checking your BIOS for abnormal cpu/system temperatures. If it's getting pretty high up there, try applying a new spread of thermal paste to see if this resolves the issue.