I just installed my copy of Risen, Vista 32 ultimate. Having the same problem as the original poster. However, I DON'T have any virtual disk emulators on my computer, and I have never had one installed in the past. I keep getting the 'insert original Risen disc' error just like the Original Poster. Not sure what else I can do at this point.

I have a WinXp 32 machine here. I installed Risen on this machine. I am able to launch and play the game.

EDIT: After successfully launching Risen on my WinXp machine and playing it for a bit, I quit the game. Later I came back to play it again and Wolla! 'Please Insert Original DVD "Risen"' - I never rebooted this machine or turned it off. Just quit playing the game, came back an hour later tried to play it again and I am now getting stuck at the disc check - very strange.

My Vista machine is a much newer machine, about a year old. I haven't had any problems running any other games from this machine. Apparently, Risen for some reason does not like my Blu-Ray DVD player.