Hi,
Run the command :
a. Type Command prompt on the start screen
b. Select "Run as Administrator"
c. Type regsvr32.exe hit enter.
d. Try to re-register. (regsvr32 %Systemroot%\System32\comdlg32.ocx)
For reference:
How to use the Regsvr32 tool and troubleshoot Regsvr32 error messages
http://support.microsoft.com/kb/249873#method3
Let us know the result. If the issue is still not resolved, we'll be glad to assist you further.