Video or heavy demand "crashing" Pc

[Grouger]

When using skype or playing wow (basically the 2 main things i do with my pc) After anywhere from 10 to 30 minutes, the programs will slowdown to the extent that they effectively crash my computer. If I manage to close the program fast enough, and wait 10 mins, the computer will go back to normal.

my specs are:
3.00 gigahertz AMD Athlon 64 X2 Dual Core
256 kilobyte primary memory cache
2048 kilobyte secondary memory cache
64-bit ready
Multi-core (2 total)
Not hyper-threaded

NVIDIA GeForce 8800 GS [Display adapter]

3328 Megabytes Usable Installed Memory

Slot 'DIMM0' has 2048 MB
Slot 'DIMM1' has 2048 MB
windows 7 ultimate

 

[Grouger]

Your pc is overheating probably.
Get some Mx-4 thermal paste and reapply a fresh dosh of it.
Remember to remove the old stuff first.

I ran CPUID monitor
and found my my core temps to be between 40-60degrees celsius with no noticable spikes before or during a crash