I just moved to another country and bought a new PC here.
When I plugged in my old HDD, Windows 7 booted, but I can not use new (wireless) mouse or keyboard on login screen. Keyboard works fine in BIOS and in Windows boot menu, but as soon as login screen appears both mouse and keyboard have no effect.
I think it might be related to the fact Windows has not yet discovered new hardware when the login screen is shown, but I do not really know. I would prefer not to buy PS/2 keyboard just to login for the first time, so maybe there are some other opions?