To everyone still having problems:
So sorry about this. This same exact problem happened to me when I got my new win 7 laptop, and after spending three hours on the phone to tech support, we happened upon the "high performance battery setting" solution which seems to have fixed it. Most of the time, when other folks have this problem, the battery fix sorts it out. On some others, though, it does not.
There are two issues with this game that cause havoc on newer laptops. One is that it is a 16 bit game. This game started production back in the WinXP days, and that system was perfectly capable of handling 16 bit. That is not the case, anymore. Another issue is that it uses DirectDraw to make the rain effects - something else that Win 7 can only handle after a bit of fiddling.
We'd really love to get to the bottom of this, but as indies with limited resources it is difficult to test this game on a large number of machines to see what works. So, here's what I suggest. Go to the AGS tech forum.
AGS is the engine that we used to make the game, and the techies there are better qualified to help you than we are. Tell them your problem, give them your specs, and see if any of their suggestions work. If it does work, please post the solution here or email it to me. That way we can help everyone!
Thanks, and my apologies again.