This has been going on for a couple months now, but it wasn't actually causing any problems, and I assumed it was a symptom of the faulty Radeon X1300 Pro AGP I got off eBay. Well, a day or two ago my X1300 Pro decided to stop emitting any video signal whatsoever. I just said "fuck it" and broke out my old Radeon 9600 Pro because I wasn't in any mood to bother troubleshooting that piece of shit again, I've had more trouble with it than it was worth. I went through the whole process of uninstalling the Catalyst drivers (as the ones I had installed were too new for my backup card), running driver cleaner pro, and then restarting and installing the proper drivers for my older card. After booting into Windows the final time, I noticed an unusual amount of color banding on my desktop, which is really weird because Windows is still running in 32-bit color mode. Checked the device manager and found that now my 9600 Pro is grouped under "unknown device". What's more, whereas the X1300 Pro still worked despite being in the wrong place, Windows adamantly refuses to load the driver for my 9600 Pro primary device now! When I check the device properties, all it tells me is "This device cannot start. (Code 10)." You might ask, what happens when I try the secondary device? Well, I don't know, because that's the VGA port and I only have a DVI cable at my disposal right now. Derp. I'm thinking either something has gone horribly wrong in the Windows registry or, perhaps more likely, the AGP on this board is going bad. I wouldn't be surprised at the latter, considering its age. For reference, this is a Dell Optiplex GX270. I'm aware of how outdated my hardware is, I can't afford anything new so I'm getting by with what's available.
The "secondary" device is a bogus entry required for multi-monitor capabilities on Windows 2000, so it can be ignored on XP and later. I'd suggest trying it on either another machine or on a Linux LiveCD to verify if it's actually the card that's bad or if it's just some weird issue in your current OS. Note that Radeon R300 support was dropped in the Catalyst drivers several years ago, so you'll need to use an older version on Windows. (On the Linux side, you'd use the open drivers, which are included with all modern distros.) EDIT: ...wait, it's an OptiPlex GX270? Those systems are well known for having bad capacitors, which may be causing all sorts of AGP issues. Check the system board for bulging capacitors. If you see any, that's probably the problem, and the system is most likely going to die soon.
The capacitors are all fine. I've been keeping a close eye on them. I can even potentially replace any that start showing signs of failure. Ideally I'd like to build a whole new system, but that's going to have to wait. Through some miracle of uninstalling and reinstalling drivers, I have working 3D acceleration again. Still a bit confused about the whole unknown device thing, but things are back to "normal" with my backup video card. The only downside at this point is that Catalyst Control Center is too stupid to see my Radeon card, but ATI Tray Tools works so I can't complain.
