It looks like the in-place upgrade from XP to Windows 7 may have messed up some NTFS permissions on your drive.
In File Explorer, open the Properties of C:\Program Files and C:\ProgramData\ folders. Go to the Security tab and make sure the Owner is set to TrustedInstaller. Also, the TrustedInstaller, SYSTEM, CREATOR OWNER accounts and the "Administrators" group must have Full Control over this folder (and its subfolders).
Check out this tutorial to understand how to take ownership and give the right permissions to a folder:
http://winaero.com/blog/how-to-take-own ... indows-10/