file under "Unkown Account" control

Alright well as put in the title I am a bit stuck, this is the third time I installed windows vista x64 bit and now im running in to having to reset file control to me when I install somthing.

Now what I mean by that is... well lets put this as easy as I can

1. install somthing by me under my account

2. file is locked

3. file owner is now under Unknown account

4. me resetting my files to my name

and im going on a virus did this And avg and avast failed to stop it
and it all started after I installed a google package being google talk, desktop search,etc after that I had all my text files on my desktop locked up and its said to unlock in 100 years...
(some program I never use that comes with vista did that.)
but now I want to install Age of empires 3 and when the files lock up it fails install so I need to know if there is a glitch that happens that I can fix or if I need to go find my copy of vista and reinstall

NOTE: I really don't want to reinstall again

anyone? no one knows?