You have to apply the res fix. Have a look here:
http://www.subsim.com/radioroom/showthread.php?t=127054 ,
http://www.subsim.com/radioroom/showthread.php?t=128723 ,
http://www.subsim.com/radioroom/show...ght=widescreen . You just want to put on the XP (assume you're running XP) file which still seems to be at
http://files.filefront.com/SH3_XPSP2.../fileinfo.html . Includes instructions IIRC. There was some discussion about putting on some Microsoft thingie, but it's not necessary.