So ive just spent most of the day troubleshooting why i can´t bind my mouse scroll and buttons 4/5.
The answer is xp service pack 2, but it must be changed for game.exe and you might also wanna do it for all users.
1. Open your diablo directory
2. Find game.exe
3. Right-click -> properties
4. Under compatibility you wanna click "Change settings for all users"
5. Check "run this program in compatibility mode for:" windows xp (sp2)
6. You might also wanna check disable visual themes and/or disable desktop resolution.
7. make sure game.exe and median XL.exe is run as admin and the usual stuff..