Resistance inside the building consists of security robots and turrets; the models inside are regular protectrons, sentry bots, robobrains, Mister Gutsies, automated turrets and one special model of the robobrain - the Masterbrain - on the same floor as the mainframe. You can turn off the Masterbrain and all other security robots in the Vault-Tec Headquarters by using the correct command on the three employee terminals in the mainframe area. Alternatively, you can destroy Masterbrain and use it to shut off all other security robots.
Super mutants have been encountered fighting the robots in the Guest Relations area. It seems they have been using the Vault-Tec Headquarters as a massing point, as gore bags, which are a common find within super mutant bases, are located in the Guest Relations men's restrooms.
A Tales of a Junktown Jerky Vendor book on a table up the broken stairs on the right side of the room, in the cafeteria area. It is meant to only be accessible when you go down from Administrations again. However, with some tricky jumping it can also be reached if you jump from the highest point of the broken staircase.
Sugar Bombs, which can be used for the unmarked quest Sugar Bombing Run, are located near the table with the Tales of a Junktown Jerky Vendor book, also in the area beyond the broken staircase.
One Nuka-Cola Quantum is located in the most Northwestern room on the second floor, It is on the bottom shelf of a bookcase. There's a door covering a hole in the floor in this room.
A Big Book of Science in the room directly east of, and connected to, the room containing the Nuka-Cola Quantum on the second floor. The room with the book should have almost no floor. When you stand looking into the room and look straight ahead at the opposite wall, you will see two bookshelves slightly off to the right on the eastern wall. The Big Book of Science is on the top one. It's very difficult to see, and the easiest way to obtain it may be to shoot it down. You can also jump onto the fridge in the room's northeast, then walk off against the wall with the shelves. You'll be able to stay on the edge, and when you get under the shelf, look up. The corner of the book should be visible for you to grab it. Alternately, you can edge close to that shelf and jump, rapidly pressing "activate".
Stealth Boy; northwest corner, top floor, in a storage closet just above the room with a random loot safe that also sometimes contains a Stealth Boy. (You have to walk around the edge of the missing floor to get to the closet.)
A pre-War book on top of a garbage can next to aforementioned safe.
The front door to the headquarters is most easily accessible from the nearby Metro Junction station.
Over the front desk right when you enter the building, suspended from the ceiling is a copy of Vault 101's door, as an example of Vault-Tec's technology.
On the Administration level there is an employee computer in which you can order Vault-Tec accessories. Upon selection of an item, the terminal will say that the item's cost has been deducted from the employee's salary. You cannot acquire these items. When you select "Vault-Tec Bobblehead", it outputs: "Only Available to Executive Level Employee."
The super mutants might be interested in the Vault-Tec Headquarters because they're trying to find another source of FEV, as it is stated that Vault 87's supply is running low.
pcxbox360 It is entirely possible that once you've killed the Masterbrain, and attempted to shut down all other robots, that all other robots and turrets will remain active and hostile. [verified]
ps3pcxbox360 It is possible to get double XP by destroying all robots then by using Masterbrain to shut everything down, on your way back/out all the robots you killed will have 1 bar of HP. Shoot them again and you will get the XP again. Robots you have vaporized or melted with energy weapons will not be revived but their inventories will be broken. [verified]
pcps3xbox360 It is extremely likely (if you have already finished Agatha's quest) that the door which leads to the mainframe can't be opened, even if you manage to get the right authorization from all three System Operation terminals. The mainframe terminal can still be accessed by entering the first floor of the mainframe room and jumping on to the pipe coming out of the wall in the south east corner of the room. From there you can jump onto the computer on the south wall. Then, looking up at the terminal overhead, jump and access the terminal while you are in the air. Alternatively, the door can be opened with the "unlock"-command when selected in the console. [verified]
pc There is a shopping cart outside the building located in between the vending machine and the entrance which, when brought to a specific spot, will disappear and reappear several times, depending on where your character is facing. [verified]