This might help from the readme:
Assertions and Crashes-Run Diablo 2's video test and make sure the game is running in Direct3d mode
-Enter a game and TURN OFF perspective
-Extract the zip into the d2folder, this should create a folder called TTD in the d2 folder.
-Run D2ModSetup.bat (should be in your d2 folder)
-Backup your D2Direct3D.dll, and rename D2Direct3D TTD.dll to D2Direct3D.dll
-If you are running D2 in the standard installation folder (c:/program files/diablo II/) you can just run the shortcut from your desktop... otherwise your going to have to change the paths on the shortcut. Use mine as an example.
-The game should load in a window with the title "Diablo II - SGDirect3d - SVR" press ALT+ENTER to go full screen, if it has not make sure you changed the d2direct3d.dll
Q: I can't even start the game! I get this error:
Halt
Location:, line #1107
Expression: Unrecoverable internal error 6fe1e115
A: You are running Diablo II v1.11 or higher (actual error numbers may change depending on which higher version). This mod requires Diablo II v1.10. Please downgrade or set yourself up for laying multiple versions.
Q: Game crashes when character loading finishes. Log file shows:
A: Install replacement Direct3D.dll (named Direct3D TTD.dll.) And run a shortcut with the extension -mod TTD -b32Assertion Failure
Location : D2CMP\SRC\CelCmp.cpp, line #1103
Expression : !( pCelFile->dwFlags & CELFILE_24BIT )
Q: It still crashes!
A: Run the vidtest and make sure you are running in direct3d mode. Sadly Glide and Directdraw will not work.
Q: The game loads fine, but I can only see my character and cannot move. The graphics are invisible/glitchy.
A: Press Escape and turn off Perspective mode.
General
Q: The game only loads in a window.
A: Press ALT+ENTER in game.
Q: My Maph@ck for 1.10 will not work, it says "invalid version" but this mod is for 1.10!
A: A side benefit of new dlls, plus if you actually ask this expect a warning. Talk of Maph@ck is not tolerated around these parts.
Q: The Barbarian/Adventurer is big and/or smelly, I want to be a sexy Sorceress!
A: You can, go to Gheed's misc page and take a looksie. I will get around to converting skills to all classes, but I need to get the skills 110% completed first.
EDIT
23rd March 07, new instructions from 0.91