Delete the D2:ED folder, reboot, shut down all non-essential programs (especially anti-virus), and re-install the game. If that doesn't fix the problem, it should at least allow you to use the un-install program to remove the game and registry entries, etc. I don't think there is much not stored in the game folder, other than the saves and a couple configuration files; in Vista / Win 7 these are located in the folder
C:\Users\ %username% \AppData\Local\Divinity 2\Savegames
