|Your keyboard must work.|
Make sure it's plugged in all the way.
- BEFORE you boot the computer if it's PS/2 connected.
Corded keyboards often develop broken wires inside the cable after they have been used a lot, or at any time if the cord was yanked on. Try another keyboard.
There is no setting that would disable a PS/2 connected keyboard in most bioses, but some computer cases have a keyboard lock switch, often a chrome one that uses a round tubular key, on the outside of the case that can disable the keyboard (if there is no switch, the keyboard is always enabled).
A corded USB connected keyboard should work while booting, but a setting in the bios Legacy USB or USB keyboard must be enabled in the bios Setup in order for you to be able to get into the bios Setup. If that's not enabled, you can connect a PS/2 keyboard, go into the bios, and enable that setting. Older bioses like yours often have that setting disabled by default; newer bioses usually have that setting enabled by default.
Tech support OptiPlex™ GX110
Manuals OptiPlex™ GX110