If you have a standalone license installed you should go to ArcGIS Administrator and Deauthorize your license. Then you would use the same ECP number you have (you saved it, right?) to relicense the software after installation.
Have you tried a 'repair' on ArcGIS Desktop from Control Panel | Programs? Should do that first over a complete uninstall/reinstall.
Oh yeah, I've tried to repair several times. I've uninstalled and re-installed Python a handful of times as well. Thanks for the reply, I didn't know to deauthorize prior to reinstall.