Lets try this then.
Go to the same folder and look for sysoc.inf.
Open with Notepad and look for this line:
msmsgs=msgrocm.dll,OcEntry,msmsgs.inf,hide,7
If it there remove hide, leaving
msmsgs=msgrocm.dll,OcEntry,msmsgs.inf,7
Close and save. Try add/remove again.
If that don't work or the line isn't there grab the file I attached. Rename it to msmsgs.inf, put it C:\WINDOWS\inf and then try add/remove. msmsgs.inf.txt