If you unplug a secondary display in Windows Vista or Windows Server 2008, and then hot-plug a display back in to the secondary port, you may get this error message: "Stop 0x00000116 (parameter1, parameter2, 00000000, parameter4) TDR_ERROR." Microsoft says they have a hot-fix for this - see their page for information on getting the hot-fix, as well as their usual warnings.