Just had a nasty fright!
1. PC was sleeping, was roused, I clicked the link to MS Word (or Powerpoint etc) and got warning box: 'application not found'. Also when I looked in Window explorer, all my folders seemed empty of MS Office files.
1b: games and media player also failed to work, suggesting a global fault, not one limited to MS Office?
1c: something called Win7 AntiSpyWare started sending strident warnings abour virus infections ++.
2. Did a full anti-virus scan with McAfee - got 2 'minor' hits that were resolved automatically. Restarted pc.
3. Defect did not go away.
4. Started in safe mode - defect remained uncured.
5. Created new user name on same pc, so that second start button appeared on desktop.
6. When I opened the new user a/c Word opened ok; worked ok; and I could open existing word files. Conclude: problem avoided.
I conclude that I originally never 'lost' any files, but that they became unassociated with their respective application.
Question: how do I diagnose the fault in the original user account, and rectify it?