It sounds like you've solved the problem somehow, but for those struggling in the future:
Try the following:
- Cut&paste (or copy-paste if you'd prefer) the D2 folder from C:\ProgramFiles\ to C:\ (I haven't noticed registry problems from doing this in the past, and worst-case you can cut&paste it back).
- Double check that the D2SE shortcut (as well as game.exe and diablII.exe; I don't think all are necessary, but you may as well) are run in compatibility mode, run as Administrator, and turn off desktop composition (I don't have Win10, so I can't tell you which other checkboxes are important, so you might have to experiment).
Here's a fairly detailed
install guide, consider checking if there's a step you missed (maybe running VidTest?).
There isn't a lot to figure out with D2SE. Once it's installed, you'll notice a Mods folder in your D2 folder, and in that Mods folder it's up to you to create a folder for HUv1.7 and place the v1.7 files within it.
i.e.
- Make a mod folder (e.g. C:/D2/Mods/HU_v1.7/).
- Expand the core-files download and package of your choice into /HU_v1.7/
- Run D2SE, select the silly HU picture, and press "start plugin" ("start d2" will not run with the mod's files).
- You might need to run the GlideWrapper test and configure it.
If you've installed D2 from Blizzard's store, then you might have D2:LoDv1.14, which isn't compatible with D2SE or HU at all. If that's the case, you can download an entire install directory with D2SE
here, and then make a folder for HUv1.7 and continue from there.