During all my mucking with installing, reinstalling, etc. my video card has been acting up (nVidia 6600 GT is the video card in question). The symptoms were that normal video worked fine, accelerated 3D (games) ran fine, but, playing AVI and other movie files would cause the system to hang for a few seconds and then reboot. By setting acceleration settings to about midpoint (disabling much of the video cards acceleration) video would play (but games would not as acceleration is required for modern games). After much frustration and mucking I finally decided to use an older driver. I went back a few revisions and things seemed to get somewhat better, but, the problem was not resolved. After dropping back to an April driver (specifically version 71.89) everything seems to be working correctly. Doh. Who’d a thunk it.