Failed 6950 to 6970 unlock. Need to flash it back.

[zack_of_steel]

So I bought the 6950 because I was told I could unlock it to the 6970 model. When I tried this today, it didn't work and, to my dismay, I found that my card does not have the 2nd BIOS switch (I had no idea that only some of the cards had them).

I am at my brother's house and I have his 5750 in my main slot and my 6950 in the second slot so that I can see what I'm doing and try and flash it back to 6950. However, my computer won't boot past the "Starting Windows" screen and I have to boot in safe mode. In safe mode I cannot run ATIWinFlash or GPU-Z, so I have no idea what to do now.


System specs:
OS: Windows 7 64 bit
Case: Antec Twelve Hundred V3 Black Steel ATI Full Tower
Motherboard: ASUS M4A89TD PRO/USB3
CPU: AMD Phenom II X4 965 Black Edition
CPU Heatsink: Cooler Master Hyper 212 Plus
GPU: XFX Raedon HD 6950
RAM: G.SKILL Ripjaws Series 4GB 1600
PSU: Rosewill BRONZE Series RBR1000-M 1000W
HDD: 500 GB SATA 6G (6.0 Gb/sec) 7200 rpm

 

[Mousemonkey]

Best answer selected by mousemonkey.