If you can’t/wont run Windows 10, all I can suggest is getting a console that D2:R plays on. Blizzard is not going to support the game running on a 12 year old unsupported operating system.
If you’re having trouble upgrading from 7 to 10, the next step is a clean installation of Windows 10. Create a bootable USB installer for Windows 10 and boot from it. Don’t forget to back up your data beforehand.