Actually if its just a matter of registry, you can remove the uninstaller info from the registry and it will be taken out of add/remove. I have to do it with Norton all the time. Norton doesnt like to uninstall completely, even with using their sysuninstaller.
In anycase, im sure other people know the location. I know it, but due to the harmful nature of registry tweaking, I will post it later if no other conclusion is found. Hope that is all right.
Remember, with all things registry, back it up first, and make sure you know what you are doing.

Bubba Gumps idea might be a little better, but it might change settings you didnt want changed.
Basic Suggestion: Perform a search of the computer for related files.
Ex. Search: Norton