Diablo Backwards Compatibility Guide

[Belix]

The folder Diablo is installed in shouldn't matter, though thanks to UAC (User Access Control) I never install games into Program Files on newer versions of Windows; the default security mechanisms can cause games like Diablo to be unable to write save files to its own folder, and they can get written out in some obscure temporary folder instead.

I don't think there's anything you should need to do with batch (.bat) files here. Install Diablo, run the v1.09 patch (as an administrator) from its own folder, then add the DirectDraw wrapper (ddraw.dll) qualakon brought to our attention and you should be good, I believe.