I have a Dell OptiPlex 960 with two graphics cards. One is a dual-head ATI Radeon HD 4670, and the other is an ancient 4MB Matrox PCI VGA card.
This system worked great under XP. I could use 3 monitors with it, with no problems at all. I just upgraded to Windows 7 64-bit, and the only card that I can see in the display properties is the old PCI card. The ATI Radeon is not listed.
Thinking that I just needed drivers, I went and checked the device manager, and there it is, with no errors or anything.
Any thoughts as to why Windows 7 won't enable the Radeon in this configuration?
(Note: Don't tell me that this configuration is impossible [at least generally], because I've been using it for years. The reason I hang on to this ancient card is specifically because it plays nice when other cards are installed. Yes, I know this is a rare situation, but it does work.)