I would say there is some permissions problem involved. I am not very comfortable with editing permissions. There is a Utility called D7 that will repair the permissions Open the program and in the left pane select Windows Repair. It is a long process though. Or, if you do not wish to do that, hopefully somebody on the forum with more experience in editing permissions can help. I personally would wait for someone to respond and use the below utilities as a last resort.
On D7, only check Repair Permissions. Make sure nothing else is checked. Then press start.
Edit: There is also Windows All-In_one repair that will reset file permissions but it looks like it gives full permissions to Users along with Administrators.
It can be downloaded from Bleeping Computer;
Edit: as a note, malware has been know to edit permissions. Have you run all the scans?
Edited by JohnC_21, 16 January 2014 - 07:40 PM.