I am so tired of buying games that continue to crash. I had a simular problem with The Longest Journey.
Don't get too discouraged. I think your video card's 3D capability is too new for a 12-year old game like The Longest Journey to recognize. As for 15 Days, it's unstable on many systems, worse than most games. I think the company that was developing it went out of business or got bought out or something and the game was rushed out the door before it was properly tested. Too bad because their earlier games did not have these problem with instability.
Hopefully what Rushes suggests will get you past this spot.