i dont know if this has been asked before but
 
after a while while playing cod 4 my comp it just shuts down by itself
 
i dont think its overheatin cuz my gpu only gets to like 80 my cpu gets to 40 and my mobo only 60-62
 
my comp specs are amd 6400+ black edition 3.2ghz, bfg tech oced 8800 ultra, buffalo firestixs 4gbs, asus crosshair nforce 590, 550W PSU
 
got watercooling in the case got a raiditor in the front with 2x 120mm fans also a fan on top of the case and one in the back
 
and with ne other game i run it never shuts down like WoW, crysis for example
 
so plz anyone that can help me out i have no idea wat is the problem

I'm running a vaguely similar system:-
 
Intel C2D e6230 @ 3.0GHz
4GB DDR2-800
NV 8800GTX
550W PSU
And yes Windows Vista Home Premium 64-bit Edition (Never understand why people slate it so much - I've had absolutely no major problems with it and it's a joy to use) What OS do you use?
 
 
I've never had any major problems with CoD 4 myself (apart from when using my Medusa 5.1 phones they very occasionally seem to randomly lose power, volume and 'richness' of sound drops until i restart the game) and I've spent over 2 days solid on that game.
 
Since you say you don't have any problems with other games I think it's fair to say that it's purely a software problem. In that case you need to ensure:
 
You have all of the correct and latest drivers for your hardware
 
Have patched CoD 4 to it's latest version (1.5 I believe)
 
Apart from that I would really know what else to suggest apart from a bad install of the game perhaps.
Very important note - I've heard that if you don't backup your online profile information when you do a reinstall you'll lose everything you've worked so hard for while playing online (Rank, weapons, perks etc.) So make sure to backup!