I have a problem which I think is related to Vsync.

When I'm in an interior area such as Megaton (theoretically), Megaton House, Tenpenny tower, the game speeds up. Speeds up as in my feet go from a slow tap tap to a quick pitter-patter reminiscent of a person tapping their pencil on a desk. When in a larger, exterior area, the game slows down to what is logical. This does not only happen in Fallout 3, but also Fallout: New Vegas (no real surprise, they run the same engine)

I have a feeling that this has something to do with Vsync, FPS, and all that other fun stuff. I have disabled Vsync through the game options and in the Fallout.ini/FalloutPrefs.ini because it would slow down my cursor and mouse movements in the game. I did use FRAPS and get my lowest FPS and set iFPSclamp in Fallout.ini to 44. This doesn't help though because my frame rate will still jump to 80, which makes the game go twice as fast.

So basically, how do I lock the FPS to 44, and not go above it.

Easy. In small interiors, there is less to render, meaning higher FPS, making the game run smoother and "faster".