PC hangs after installing GPU

I hope I can get a solution quick so I'm turning to you guys.
See, a friend of my brother bought my 8500gt.
My brother helped him install the gpu.
The mobo is an ECS p4m900t-m, and my bro uninstalled the VIA display drivers (on board GPU is VIA's) through add/remove programs in control panel.
Then without running Driver Cleaner he installed the gpu and the drivers(182.06) in safe mode.
Turned on, everything was ok. Even managed to play Hitman3. Then turned off and both of them went out and played basketball.
Then, just now, the guy called up and told my bro his PC hangs every time after boot up(stalls at the 'welcome' frame).
So what you think?
Was it because he did not run Driver Cleaner, conflicting drivers, or maybe theres something with the mobo and the drivers? Or maybe other things?
Or may you guys suggest some steps to try out?
I can't give his full specs right now.
Forgot to mention that his OS is XP 32bit.
Mobo as stated, 8500GT, Core2Duo not sure which model but my bro says it runs at 1.8Ghz, so dunno which model for there are a few C2D's running at 1.8. This is what I can give right now.

PS: Some details of the mobo here.
http://www4.dealtime.com/xPF-Elite [...] 0-100-Ethe

double bumps!