Sometime certain Microsoft Libraries can become unregistered when installing and uninstalling a lot of software. One very common problem is the MSCOMCTL.OCX.
To correct the error, first search your drive for MSCOMCTL.OCX to see if you have it. If not you can download it from HERE
The file should be placed in your C:\WINDOWS\SYSTEM directory. Or, if you are C:\WINDOWS\SYSTEM32 if you are using WinXP.
Once it is there click START--> RUN and type "REGSVR32 MSCOMCTL.OCX" (No quotes) in the box.
That should fix the problem.