Just got my char almost "killed". There's some conflict between Iron golem and Mercenary sections. There sadly no backup or broken save file so that's what i did: Respec skills and save char (golem was summoned and mercenary dead) Then game was keep saying me "bad mercenary data, cha...
With the recent patch, I managed to load my Zon, but once I put in a couple of hours, she no longer loads. Probably has something to do with the items.
From what I ascertained from Tom1986's suggestion, and from my experience after following the latter, you would have to have the launcher running, but open the game from the original D2 executable, provided that the two files are within the D2 directory.
I did exactly everything you instruct. I managed to get the game running up to the main menu, but when I tried to create a new char, a "generic bad character file" error occurred.