|If you have a USB keyboard you may not be able to enter ANY keyboard commands during the pre-Windows start up. |
That is due to USB not being supported without a BIOS setting being enabled. Unfortunately your BIOS most likely defaults to disabled for the "enable legusy USB devices" setting.
That would occur because when the CMOS battery went dead the BIOS settings automatically revert to the defaults.
You need to at least temporarily connect a PS/2 keyboard in order to enter the BIOS and reset MANY settings there.
As long as you maintain power to the computer the setting will hold. The CMOS battery only is needed when power to the computer is removed (power strip, etc.).