Hi,
Right click you "Desktop" click "Properties" and then change your "Themes" to something else and try again.
If that has not fixed your problem, you may have a virus or malware Go to:-
http://housecall.trendmicro.com/
or:-
http://security.symantec.com/sscv6/WelcomePage.asp
Download and run to remove any viruses you may have. (Sometimes a virus will stop you accessing an anti-virus site, so try going through safe mode (Tap F8 on boot up) and see if you can access it there.)
Then go to :-
http://www.malwarebytes.org/
or;-
http://majorgeeks.com
Download, run then quick check your PC for any problems, if still there do a full scan.
If that has not helped, then maybe a Windows repair is required. If you want to repair your installation with your OS disk, go to:-
http://www.daniweb.com/forums/thread148706.html
Post #7