1. File and directory permissions.
Read http://www.mxmania.net/Tutorials/tutorial_Ntfs.htm
2. The registry has similar permissions and ownership. Use the lesson in item one and this.
http://www.geocities.com/kilian0072002/registry/lockreg.htm
3. Manually uninstalling AVG (from the AVG forum...) read
http://free.grisoft.com/doc/5466/lng/us/tpl/v5
Bob
I had to perform a system restore. After that I had to reinstall McAfee system protection. The virus protection part of the program will not install until I unistall AVG 7.5 from Grisoft. Sounds easy enough right? Too bad I cannot remove AVG because it is "write protected" or "read only". Any ideas fellow CNET fans?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic