Over 3 years ago. Lol. I ran into the same issue recently a figured out a way without trying to fiddle with a PS2 keyboard (on a non PS2 mobo) or removing the battery or messing with jumpers. On my particular motherboard there are 2 USB 2.0 ports. Facing the ports, the TOP RIGHT USB PORT takes priority. I had my mouse plugged into this one. Plugging my keyboard into this port granted me access to it during startup and I was able to press DEL or F2 to get into the BIOS. Crazy!
As far as I know, depending on the mobo, it will always be either the top right or the top left USB port. Do not restart your computer if you feel like you have chosen the wrong one. Power it all the way off and try the other port, then power it back on. Restarting will not allot you enough time.