Need Help Bad

I have been having problems with my computer/drivers/videocard. Anytime I try to shut my computer down after it has been on for a while it will blue screen. Power_driver_state_failure. I have done some research and read some forums. It turns out to be a video card driver problem. I have downloaded the newest nVidia drivers (186.18) and when i install them they crash my computer and when it restarts it blue screens and continues in a cycle until i go into safe mode and delete the drivers. The only drivers that i have ever had some luck with are the 182.50. They still manage to blue screen when i turn off my computer of course. but at least i can use my computer. any help on what to do or going in the right direction would be amazing.

RIG:
Crosshair II formula (1502 bios)
OCZ 1066 8gb reaper
PII 940 BE (stock voltage)
Zotac Gtx 295 (182.50)
Xclio 850 module power supply
windows vista ultimate 64-bit.

Im tired of trying everything known to man. I have installed many drivers. Always deleted the drivers in safe mode. Got all the drivers from the manufactures site.

please please please can someone offer some advice. i have spent alot of money on my system. it plays games amazingly well. but it wont shut down.

I didn't really know where to put this. Im new to this site and created an account really fast and just posted as fast as possible. You have no idea how pissed off I am at this build.

how do i go about installing vista again? and how do i turn off the auto update because i do hate that feature.