If you get the game on the pc, can it hold more than two profiles with different saves?

There are no profiles really, just saved games. You run the game and pick what save you wish to load.

So, if two people were to play, they would have to use seperate save files?

There can be hundreds of saved games.
I have not tried it myself, but I would guess that when logged into the PC under your own (non-administrator) account, the game can only load from your own personal documents folder (where the game stores it's saves). In this way, the login serves as a kind of profile. (Though I'm not actually certain if Fallout 3/NV would play using a non administrator account ~I've never tried.)

An administrator could load anyone's game if they really wanted to.

Yes, and it plays normally on a non-admin account. One thing I would like to see, is a better character-management capability in the game. Instead of a huge long list of all your saves, with every character's save files all bollixed up together in a big mess, they should first have a character-selection screen, where you choose which of your chars you want to play. This screen would just have a picture and name of each char, in their current gear, with their level and date of last save under each picture. You could either click directly on a char's picture to launch that char's latest savegame, or click on a button under the picture to open up a list of all the savegames for just that character, complete with savepoint screencap pictures like we have now. This would be a huge ease-of-use improvement over the current method.