Welcome to the boat mate.
Check out this thread.
http://www.subsim.com/radioroom/showthread.php?t=155786
Be advised that you can run an environmental mod with the stock game ok but you can not run one with the bigger mods like TMO, RFB or FOTRS.
Also check out this thread for some very good playing tips etc.
http://www.subsim.com/radioroom/showthread.php?t=146795
Magic