This can be caused by malware (virus/spyware) or may simply be caused by an unregistered dll library file.
To re-register the files, click on the Start button, click Run, then type cmd and click OK or press Enter. In the command prompt window, type regsrv32 themeui and press Enter, then type regsrv32 /i shell32 and press enter. Reboot the computer for the changes to take effect.
If this does not fix the problem, you probably have a malware infection that needs to be removed - do a full system scan with good virus and spyware removal tools. If you don't already have something installed, I prefer Avira AntiVir and Malwarebytes (both are free and work very well).