if you have a legit CD key you can go to https://us.battle.net/login/ and create a Battle.net account and add your cdkey to the account and then download the D2 and D2lod installers, They are single files that you can just keep somewhere on your comp and run them anytime to install D2 same goes with all blizzard games from Warcraft 2 and up but you have to have a legit cdkey for each game, also by my guessing all Cdkeys from warcraft 2 up will have to be added this way when Battle.net 2.0 is released, im quite sure you will use a single account on Battle.net 2.0 and it'll be your Battle.net account, they have already forced WoW accounts to be merged into a battle.net Account [FYI]