Hello,
I have discovered that if trying to remap buttons on the wireless xbox 360 controller for windows, the buttons that do not respond and cannot be remapped are the "Back, Start, X, Y, A, B" buttons. Everything else on the controller can be remapped no problem, but for some reason those buttons simply do not allow remapping. When the asked to "Press any button" for the first time all the buttons work and are present, but as soon as you try to remap any of the ones in question, they get lost and can no longer be remapped.