Originally Posted by Muppet
Where is the Doom level part of. I haven't come across it yet.
It's in the gearhead vault. The door for it is right near the entrance/exit to the level, I think the first or second hallway you go into after entering the level. It's a got a grey box in front of it and purple letters painted on the door. To unclock it you have to activate the computers in the office all the way up on the top floor of the level. Just press E on each of the computer keyboards, you will hear a gong sound with each computer activation, and when all are activated you can hear the door click and unlock. Then go all the way back down to the start of the level and find the door, which should now open for you.