I found a solution to the problem and I have the game installed on a non-default location on my C-drive

I don't know how many of you use no-cd cracks to silence your computers and skip the work of finding the box and putting in the disc, I at least hate that procedure and therefore thank the pirates for making it possible for me to run my Pc games without putting in the disc every time (this is one of my most hated parts of being mainly a console gamer xD).
So if you haven't figured it out yet I would suggest you see what I wrote in this same-themed post: http://www.gamesas.com/forums/viewtopic.php?f=40&t=21146&p=235065#p235065

I hope this helps those of you who also skip the disc-check

(this is why I love Steam btw

)
EDIT: User Kanoobi let me know in the linked post above that a crack is not even needed to run the game without the disc in... so now I'm not sure if I by assuming that it was necessary created a problem for myself by cracking it...

Oh well, in that case I guess people should do as the other user ifritgr says in his post right after mine in the linked thread.
No need to crack... that's new for me... :S