never had the problem with the Radeon X1900 XT or Radeon HD 3870. i use AMD/ATI's uninstall utility from the Control Panel->Add/remove Programs, and then Driver Sweeper 1.0 and 1.5. Then reboot into safemode and run both versions of Driver Sweeper again before finally rebooting and installing the fresh drivers.You say that you've "unistalled/reinstalled the driver multiple times now...". Have you completely removed all traces of ATI with something like DriverCleaner, for example?
I had that problem a few years ago with an older product and I had to clean everything out and start fresh.
Did this problem occur after installing new software? Hardware? A Windows update? Can you try the card in another system?