No problem at all here. I have about 2 times the FPS of windowed in fullscreen (has to do with ObjectDock and Samurize).
But that in the end does not make much of a diff, 360 vs 700 on 60hz screen does not mean much :)
But on your problem: What kind of graphic card does he have?
I ask because it would be possible that the window mode runs in 16bit, while the fullscreen goes to 32bit (older hardware did not support 3D 32bit windowed mode) which results in the difference you are seeing.
But that in the end does not make much of a diff, 360 vs 700 on 60hz screen does not mean much :)
But on your problem: What kind of graphic card does he have?
I ask because it would be possible that the window mode runs in 16bit, while the fullscreen goes to 32bit (older hardware did not support 3D 32bit windowed mode) which results in the difference you are seeing.