Try using Gameshadow to check to see if you have the latest video drivers. If not, have Gameshadow install them for you. You may also try reinstalling the game from scratch and re-patching it up. Also, try lowering the resolution that you run the game. Go into the Silent Hunter 3 folder, then into the Data folder, then into the CFG folder. Look for the file Main CFG. Make a backup copy of the file and then open the original file in Notepad. Look under video. You may be running the game at too high a resoulution (I don't know why, but the game defaults to some crazy resolution that doesn't work on a lot of machines. Mine included).
Try lowering the resolution under [VIDEO] in the file.
These are my settings:
[VIDEO]
Resolution=1024 x 800
DynamicShadows=No
FullScreen=Yes
Synchronized=No
ParticleDensity=100
TextureResolutionHigh=Yes
If this doesn't work, also try lowering your actual screen resolution (You can change it back after you get the game running).
If all else fails, there's always Ubisofts (cough ! Cough) award winning (cough cough expletive muttered under breath

) tech support.