What happens when you try to start the game? (nothing, error message, crash...)
Did you install the patch before or after upgrading to Vista?
Did you run the Starforce removal program (see
here) to remove the drivers after you installed the BD patch?
In Windows Explorer, can you browse to the 'Beyond Divinity' folder and double click on the div.exe file to start the game directly?
You could try a clean re-install of the game and patch, using Lady Rain's advice above to avoid having the Starforce drivers try to install.
Zip or otherwise backup your saved games folder to another location first, just in case. Each save is a separate subfolder in the '
..\Beyond Divinity\savegames' folder; the 5 '
bd_act#_start' folders are created/updated by the game/patch, and do not need to be backed up.