Help! Possible VidCard/ hardware Issue

Ok, getting desperate here, any help would be appreciated.

I had to reassemble and reinstall my pc and operating system recently and now i have 2 problems.

1. if i install my video card drivers(only tried last version, 6.3) my pc will freeze and reboot as soon as any kind of animation (apparently) is loaded, eg. i load a website which has a piece of flash running, which virtually renders it useless. At the moment i am running without video drivers installed until i determine the issue.

2. Since i made a fresh install of windows, i am now obviously downloading the security updates. If i download the second batch of security updates (a total of 40 updates, automatically downloaded and installed), once pc reboots it arrives to the windows logo and then reboots itself every time. I even notice that before the reboot happens, it seems to switch off power from the mouse and keyboard, i noticed a blue screen for a split second once when this happened.

I have now restored to before the security updates were installed and i can boot up and browse net etc (although with high vulnerability) and no video card drivers installed. I am downloading service pack 2 and will install this instead of all the security updates which come before, maybe i can avoid the issue this way.

One last point, i think i had this problem once before, especially the video card freezing problem, but i do not remember how i had managed to resolve it.

My system specs:

Asus A8n SLI nforce4 mobo
1GB Corsair low latency ram
Ati x850xt 256mb vid card
Raptor 10,000RPM 40gb SATA hdd(windows installed here)
Seagate Barracuda 40gb IDE hdd
450W Enermax PSU
6+ fans all around cooling away

I tried to keep it "short" for now, will post more if ppl reply, help me guys, i am at a loss at what to do to solve this at the moment. Thanks for reading till the end!