SH3 requires CPU and RAM. Technically speaking you need 1GB of RAM to play it but you can get away with 512MB if you have enough CPU power. I have a 3.3GHz with 512MB RAM and SH3/GW/GWX work fine. When you're in places with heavy graphics like harbours convoy attacks etc the game can be a bit slow some times but it general you have no problems at all.
As far as GW is concerned if you have problems with the game just don't install the sea floor mod. That usually does the trick
BTW of a funny note follow AVGW advice and leave SH3 now. Get a girl and stop the game. It's too addictive and it will ruin your life
:rotfl: :rotfl: