Re: GTX580 - Games Minimizing !
I said it could be the PSU, you need to figure out if the problem lies with the PSU or the video card. I know it's a hassle to troubleshoot but if updating your motherboards bios and putting your CPU back to stock clocks has not solved the problem, you may need to fork out the money for a new PSU to determine if the video card is faulty or not.
A PSU can overload or fail at any time, I had a new unit that barely lasted 5 months before becoming unstable, the system would completely lock up while playing games sometimes it took an hour sometimes 5 in the end I had to rma the thing and buy a replacement.
I have just got a GTX580 myself which is why I'm curious about this problem, the only thing I can think of is it could be the new power regulation these cards have which is forcing games to run in windowed mode to prevent the system from becoming unstable.
Anyhow the last thing you want to do is replace the card with another one only to find out your system is still unstable. Good luck and let us know how you get on.