I think you mean MSCOMM32.OCX, it's a Visual Basic file that is either missing or needs to be re-registered. You can download it here
http://www.ocxdump.com/download-ocx-.../download.html
If it is only when you try to run a certain program then put it in that programs directory, if not then put it in the system 32 folder if you are running XP.
You could do a search for it first if you like and if it's found then you will need to re-register it.