To note, if you want to make additional installs, you need to delete the Diablo II installation entry in the registry. This will allow you to make additional installs as normal.
I have addtionals installs of D2 and I havent changed anything in registry. When you install a new copy of D2 change your diablofolder to Diablo2 1.12 or something and only switch out the names when you want to dip into other versions.