General Questions, would like to be pushed into the right direction.

[SgtBen]

Hey guys, appreciate the time you take to read this or even look at it. Id like to ask a few questions recently got my card its awesome and does exactly what i want it to although, i know theres a lot of topics on this but i was on COD4 today and as you know the screen goes blank you can still hear whats going on around you but then the image will reappear and carry on as normal, i was looking around and i downloaded the hotfix hotfix_vista64_8-471-1-1-080324b-61161, that didnt fix it ive downloaded 8.4 earlier today was on cod for about an hour and it seemed pretty good nothing happened untill it froze and i had to reboot the PC, I'll do a few more tests see what happens and i'll report back, also another thing not sure whats happening but im not to HOT on overclocking but i know the basics I try pushing it up to about 3.2 3.3 ish and my computer boots i load a game it lasts about 3 mins before it shuts down and disaproves, hard to get it stable i know theres more to overclocking than that and to keep it stable etc with volts and so fourth i'll link my system and can you guys send me in the right direction on whats best to do with my system as it stands and what i can get out of it and whats needed for it to keep stable.

1gig x2, 2gig of DDR2 Geil duel channel ram PC 6400 800mhz timmings 4-4-4-12
Radeon HD HIS 3870 IceQ3 GPU clock 825 mhz, Memory clock 1250mhz
Intel Quad core Q6600 at the moment on about 2.72
OCZ Stealth X Stream 600w Multi GPU PSU
ASRock 4core1333-viiv Motherboard
Asus Silent knight II CPU cooler
Samsung 250gig SATAII HD / 500gig samsung Barracuda
Samsung Syncmaster226cw monitor at 1680x1050 res
Antec 900 case
Vista ultimate 64bit