I recently picked up AVG antivirus. When I loaded it up, it pretty much said C: = VIRUS OSHIT!
I shut it off, didn't try to quarantine/fix anything.
Now when I try to open most applications (media player, AVG, Dwarf Fortress) I get an error saying the parameter is incorrect.
I can't even uninstall AVG.
Another error that I'm getting is that I don't have permission to access my programs.