Autonomously disappearing and resurrected files and shortcuts

Forgive me if this issue has been covered before. I am new to the list but
couldn't find reference to it in older postings.

I have had instances in which (1) files I deleted off the desktop reappeared
after the next reboot; (2) entries in my Start menu disappeared with no
action on my part, and (3) favorites in IE8 reappear when restarted although
I had deleted them in the previous session. Can anyone explain why this
happens and what I can do about it?

Paul

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Paul A. Crable
Portland OR USA