Do a "clean install" http://forums.adobe.com/message/4041846
If that fails, download this file: Take ownership.zip
Unzip it, and double click the ".reg" file it contains.
Click "Yes" and "OK" to install it.
You will now be able to take "root level" ownership of ANY file or folder on your system.
Right click your C drive and select "Take Ownership".
A command prompt window will open as the new permissions are applied. (It takes a while to do the entire drive)
Once it's finished, you can modify or delete any file or folder on your system.