MysterD's Installation Instructions for...
Diablo 1 (without Hellfire) via Belzebub Source Port:1. If you still have your retail copy and a CD/DVD/BR drive, then install the Diablo off the CD. Should take no time.
If installing on newer Windows OS's (i.e. W7 and above), don't put it in protected folders - i.e. C:\Program Files (regular) or C:\Program Files x86. Anywhere but those.
Try elsewhere - i.e. C:\Games\Diablo; C:\Diablo; or anywhere else that isn't protected folders.
2. Copy DIABDAT.MPQ file from your CD over to your Diablo folder where Diablo.EXE resides.
You'll need this to run the game without the disc, whether natively or via Belzebub.
3. Patch it up to 1.09 (regular) - these files should be on Battle.Net or Lurker Lounge.
Battle-Net Link for Retail version patch -
https://us.battle.net/support/en/article/200684Lurker Lounge link -
http://www.mediafire.com/file/5daws9f531q51zr/drtl109.exeDownload the patch from one of those places and install it.
4. Patch it up to 1.09B - these files should be on Battle.Net or Lurker Lounge.
Lurker Lounge link -
http://www.mediafire.com/file/4c7jk35jtjjom3e/drtl109b.exeDownload the patch and install it.
5. Grab Belzebub Source Port (i.e. Diablo 1 HD Mod) and download it.
Get it here -
https://mod.diablo.noktis.pl/downloadThis Source Port can only be played Offline in Single Player Mode.
This Source Port also includes also extra classes, unused content/quests, zoom in/zoom out features while playing (roll mouse-wheel up+down), high resolution support (including 4K, if you want to go that high), FPS caps up to 60FPS, etc etc.
6. Unzip and dump Belzebub's folder contents right into the main Diablo 1 folder (where Diablo.EXE is).
All new files here (except README.TXT), so it shouldn't over-write anything.
7. Boot game-up from running Belzebub.EXE.
Also, you might want to create a shortcut for Belzebub.exe and throw that on the desktop.
8. Enjoy D1 at High Res + on modern systems!!!