Fujitsu Lifebook Windows7 Pro 64, current model, good condition, up-to-date anti-virus s/w, no known malware history.
Starts up apparently normally but ceases to respond once reaching the login prompt - no response to mouse and keyboard.
External mouse tried - still nothing, machine doesn't appear on network scan.
All hardware works normally when booting from Linux trial image.
Recovery disk applied - detects no startup problems, system restore by several days resolves problem.
Run ChkDsk and SFC /scannow without issue.
After 2 days of normal use the same thing happens.
Suspect a corrupt Windows update file - but how to clear?
Recovery disk now says that Windows not same version.
Boot menu system restore now says no system restore points found.