There is a simple trick that makes the game show the information about unregistered copy.
How to Do This?
- Beat any chapter and go to the hub level.
- Open the console by pressing “~” (under Esc), then type “sv_cheats 1” and “noclip”.
- Go through the locked door and get close to the teleporter.
The game will still show some tutorial stuff if you choose the path to the first chapter but also it will start showing information about unregistered copy.
- You haven’t registered Quake!
- Call 1-800-idgames to unlock the full game from CD-ROM or for mail delivery.
If it doesn’t show up, walk around or go through the door several times and it eventually will.