AMD/ATI catalyst & driver failure
The other day AMD popped a message up on one of my boxes asking if I wanted to update the management/driver software (Catalyst), so I said "OK".
The update failed towards the end so I rebooted, and was greeted with a black screen and a plaintive "no signal" message from the monitor.
Fortunately (?) the MoBo has an onboard AMD 4250 chipset, and connecting to that got me a visible screen and a pop-up warning that there was no AMD Radeon driver loaded. Obviously the image was very low resolution and the system was using a Windows 7 default driver.
Sooooo................ I downloaded the upgrade from AMD's site and ran it.....................no joy, and on top of that the damn thing was trying to update the HD 4250, and ignoring the HD 5770 card that was installed.
Sooooo................ I replaced the HD 5770 with an HD 5670.......................still no luck!
I used the AMD uninstall software, then ran a registry cleaner then rebooted............nope!
I removed the software again and ran the Sapphire CD installation disk (both cards are sapphires BTW)......... it "said" that it had installed successfully, but only for the HD 4250 onboard chipset.
I finally downloaded "DriverSweeper" and deleted all things AMD; then re-ran the Sapphire installation CD and now everything works fine with the HD5670.............. not the sharpest tool in the box but it does score 7.0/7.9 on the WEI (the HD 5770 scored 7.4)
My "plan B" is on the floor next to my chair.................An Asus GeForce EN210..................... cheap and cheerful but couldn't give a rat's ass about AMD/ATI drivers :D............. I didn't have to go that route as it turned out, but I might have if there hadn't been onboard graphics, as Windows 7 didn't use a default driver for the HD5770.
My recommendation is to get a free copy of "DriverSweeper" right now, as they have been taken over and you have to pay for the replacement. It is still the same team though.
My other advice is to NOT let AMD update your machine, as they are obviously doing it on-the-fly or in "realtime", which is not a good idea IMO. Better download the software to your HDD and run it from there.
Hope that is of help/interest :)