Computer holds when certain games played

System specs:
Asus A7V8X-X Mobo
Athlon 2600+
Windows Xp Pro
Kingston DDR400 512 ram
GeForce 6600 256mb agp8x video card
410 watt power supply
20 gig hdd (about 7-10 years old)
30 gig hdd

Hi, I'm new to this forum, but hopefully you guys can help me out. I have been having a problem playing some games on my computer for about 6 months now. Only when I play certain games, my computer completely freezes. I had my cpu overclocked to a 1.9ghz but now its back to a 1.5. Whenever I play games that use crappy graphics, its fine, but it is also fine during Doom3. However, when I play games like Warcraft 3, Starwars Battlefront, Dungeon Seige 1, and Unreal Tournament 2004 it will just hold indefinitely. I have to completely reboot the system. I reinstalled windows and the games themselves, but they still won't run. I'm out of ideas. Can anyone help me?
Edit: I forgot to say that it also holds when I watch the visualization "Milkdrop" on winamp for too long.