You more then likely saw a bad install o start with for some reason. That may have been a result of any av program or firewall you have on being enabled during the install itself.
Fortunately DarkNovaGamer wrote up a guide for seeing the beta version uninstalled. Internet Explorer 9 - Uninstall
and note the other information posted by Airbot as well. Uninstallation of IE9 and flash square
Why you ran into that particular error however has mainly to due with the WGA and the Windows 3.1 or 4.0 installer. You likely need to go for that and try again later once you have the present install raken care of to see a amooth install if there are any other problems being seen.