u need to set the cdkeys into the .reg file (save n then import the key into the registry)
then run the refiller n select your d2 folder.
now u have just set up your first pair of cdkeys (d2+lod) which u can use by using ur normal shortcut pointing to d2 loader (not game.exe)
now open the same .reg file n enter your second pair of cdkeys. save n import.
run refiller n refil both cdkeys but save them in a notehr folder, select a name like cdkey2.mpq, then copy them into your d2folder.
now create a shortcut with the following argument (i think thats the right word) "url" -mpq cdkey2.mpq
that shud do the trick, now u can have 2 versions of diablo running at the same time.