-FIRST- I HAVE NOT tried this code nor do I confirm its functionality.
Go to your diablo 2 shortcut on your desktop or wherever your shortcut is. Right click it and click porperties. Now go to the menubar marked "Target" in that bar, type "-act 6" in AFTER the quotes which contain something along the lines of "C://Program Files/Diablo II". Your bar should now contain: "C://Program Files/Diablo II" -act 6
Thats it. There are many suffixes that you can add here are a few: -lq (Low Quality) -multiclient (Let's your play multiple programs of Diablo II at once) -w or -window (Window mode)
Thats about all I got, if you want more go to the Blizzard website at [link]blizzard.com[/link] or check the Official Diablo 2 Guide at [link]www.battle.net/diablo2exp[/link]