Hi.
Was the G15 keyboard a PS/2 or USB model? When you switch on your system, do the keyboard status lights (Caps Lock, Num Lock, etc) blink? If not, the keyboard either isn't working or isn't receiving power. Try an alternative USB port. If you have got a USB to PS/2 adapter supplied with the replacement keyboard, try using the other interface. In 'Device Manager', uninstall the keyboard driver so that you are left with the generic driver as supplied on the Vista installation disk. If none of this works, then it is possible that the replacement keyboard is faulty.
Dwarf