Freezing problems.

hi there.
after five minutes of playing games, my computer will freeze. the games i've tested are the ones that i'm bothered about playing: Painkiller, Guild Wars and Half Life 2.
there's no BSOD, just a complete lockup.
also, occasionally, the computer will freeze when accessing a CD/DVD once i've placed it in the drive (it has yet to happen to a disk that was already in the drive whilst Windows booted up).

Computer:
Pentium 4 3.2
1+gig of RAM
SATA hard drive
6600gt 256mb graphics card.

my graphics card is new but i do not think it is this as my older card, a Radeon 9800 also began locking up just before i upgraded.
i've upgraded all the drivers that i can think of.

are these problems connected? any ideas on what they could be?

Probably heat-related. Games place a heavy load on the CPU as well as the graphics card, leading to an increase in heat output. Too much heat can lead to malfunctions, even before your motherboard's thermal protection kicks in and shuts the system down (assuming it's turned on). If your fan and heatsink is clogged or failing it can lead to these sort of problems. Check to see if the heatsink and fan vanes are clear of dust and gunk. Also, try taking the heatsink off, cleaning the thermal paste off (use lighter fluid, naphtha, isopropyl alcohol or whatever), and put a fresh layer of Arctic Silver on the contact surfaces. Failing that, replace the heatsink and fan altogether - they don't last forever, especially the crap fans that Intel bundle with their processors.

cleared out my heatsink and the fans, resurfaced the heatsink and bought another fan.
so far so good, thanks for the heads up. :)