AMD Drivers Suddenly Broken on Upgrade

Until recently, I had two Gigabyte HD 6850s (no CrossFire) in one of my machines and an HD 6950 in another. Well, the two 250mm fans in the 6950's case both died within a day of each other, and of course replacing them would cost as much as a decent new case...so the 6950 hadn't been used in a while. I also realized that perhaps this "CrossFire-ready" budget PSU is probably designed for two 6450s and not two 6850s, because the machine would not run at all smoothly unless I really downclocked one or both cards. It would often just turn off without warning. It was obviously the GPUs drawing too much power, so I swapped them out for the one 6950.

I had Catalyst 12,10 installed, if I remember correctly, and had never gotten any BSODs or other obvious signs of driver incompatibility or corruption. I'd upgrade whenever a driver was released that didn't actually hurt DP performance and never had any issues.

Until I installed the 6950, at least. Now the machine won't even get to the login screen unless I am in Safe Mode. The screen glitches up as though the card is fried (it is not, for the record) and I get a BSOD specifically naming atikmpag.sys as the culprit. It does a memory dump and reboots.

I have yet to analyze the crash dump itself - working on it.

The most irritating and frustrating thing is that, since I assume it's a driver issue, I try removing the drivers only to have Windows immediately install them again and not allow me to stop the installation at all. I was told to use gpedit.msc to prevent this, but this particular machine runs Home Premium, which does not have Group Policy Editor. I tried "deleting" the drivers during uninstall (which as it turns out doesn't really delete them) and immediately rebooting to normal mode, only to have Windows immediately install the drivers again.

So the drivers Windows automatically installs (and for some reason thinks are the best for my 6950) are dated 25 April 2012...so um no. Even if I try and install Catalyst over them, the system won't boot into anything but Safe Mode successfully.

Frankly, I am at my wit's end here. I don't have the patience to manually replace individual INFs or what have you, nor can I justify the cost of a better PSU to resume using the two 6850s instead. I read a lot of threads out there like this issue, mostly from a year ago or more, and saw a lot of fixes involving uninstalling SP1 (and putting it back after drivers installed) and lots of clean Windows installs. Of course, I don't know where I wrote down my product key (I know I can find it out easily) and the best part is I don't have Windows 7 install media at all.

Of course I can't install Catalyst in Safe Mode (but I can somehow uninstall display drivers). I'm stuck.

Am I missing/overlooking something, or is this really as complicated and frustrating as it seems?

Thanks in advance for any insight you may be able to offer on this...I appreciate it.