Glad that you worked your problems out. For those that are reading this post at the moment:
You can remove Demigod through the add/remove programs in the Control Panel.
But...When I was trying to uninstall the beta prior to installing the complete version, the game didn't show up in the A/R. Revo didn't even see it. (very odd)
Luckily, there is an uninstall feature in Impulse, through the 'my games' tab. I used that, and it worked like a charm.