One other thing you can try is to manually edit the registry yourself and delete any key that is in reference to that program OR the manufacturer.
BUT, for gods sake, DONT do that unless 1) you have made a backup of your registry! 2) you have a good idea of what you are doing in there
If you meet the requirements listed above......
I have successfully corrected several problems with bad registry settings before by doing a search for the following; manufacturer name (ex. symantec for nortonAV), then doing another scan using the products name (ex. word for MS word), and then searching for the location where the program was installed (ex. c:\program files\norton for NortonAV).
With your backup in hand, delete the keys that closely match the program that you are trying to clear out. Once you are done, restart the computer and reinstall the program and see if it worked.
BTW it is a great idea to uninstall the program before you try this step