Corrupted Registry--Win XP Pro

I had a program, the name of which I can not remember, that I concluded was little better than the spyware it was supposed to remove (among other actions it would take), so I got fed up with it and completely eliminated all references to it everywhere. Apparently I eliminated something wrong from the registry. Now when I try to install software it sometimes comes off without a hitch. Other times I get an error message: "The procedure entry point CallWindowProMF could not be located in the dynamic link library user32.dll." Replacing the .dll had no effect, and I finally realized the expression which hopefully is dark red belongs in the registry. Searching the registry revealed no finds. Unless somebody has a better idea I need to know everything there is to know about CallWindowProMF in the registry: keys, values and, that other thing. Somebody, please help.