I know the title is kind of "noobish", but I really don't know what else to do.

I recently bought my MSI GTX 560Ti mainly for playing Battlefield 3. The joy of playing with nice graphics soon vanished, because the driver kept crashing and thus prevented me for playing longer than 30min...

I looked through endless forums for a solution and after a while I came to the conclusion that this was a proper fix:

1. Increase the card voltage using "MSI Afterburner" to 1.065 (I dont know the exact number, but it was something close to this)
2. downclock the chipspeed to 840mhz.

This initially worked, until the game (and/or nvidia driver) crashed and forced to pc into an instant reboot. Now it seems the gfx driver crashes on the first windows symbol (when the 3 dots form the "flag") - the picture is scrambled with green pixels. Windows starts, but only on 1280x1024.
The Card is not recognized on Afterburner or Dxdiag.

I tried reinstalling the driver but with no luck. Have I destroyed the card by upping the voltage?

I have tried installing my old GTX 275 and it works fine...so it doesnt seem to be a software problem.

Setup:
MB: Gigabyte P55A- UD4
CPU: i7 860 2,8 ghz
GFX: MSI GTX 560 Ti
RAM: 8 GB Corsair Dominator XMS 3
PSU: Corsair TX 650 W

Thanks in advance!