Comp runs videos like crap, bad HD? Bad Processor?

My computer has been running videos terrible lately. For example I downloaded a video for crysis and tried to run it. Its hd 1280X1024 or something and it runs terrible. It also uses 100% of my cpu. It basically play the audio in the background then, plays like 3-4 frames and stops for 10 seconds, skip plays a few frames, then stops again.

Is this a cpu problem or a HD problem? Or maybe a video card problem.

Background.

Athlon XP 1.4ghz
768mb Ram
80 Eide Hard Drive
Radeon 9600se 128mb
hard drive was just formatted 3 times acctually

Thanks for the help.

P.S. Will a sata raptor run better than an ide drive off of a pci sata controller? (no sata on mb)