My only advice to you would be to install this program called [url=http://www.sysinternals.com/Utilities/Regmon.html]REGMON[/url] from Sysinternals.

Run Regmon. Now try to reinstall the program and watch for the registry keys that are accessed. You can view the log for keys that were "Accessed" but not "Created" which would mean the program looked to see if the key existed and then made a decision to install or not.