This is rather obsolete machine but it happens to house my home server. For similar reasons one might need it to boot with nothing but a network cable attached. If that is the case this particular beauty will complain about "No Keyboard Found" and will offer you to hit "F1" to boot. Of course when there is no keyboard attached to a computer - the most logical thing to do would be to hit a key to boot. Now to get rid of that annoyance is rather counterintuitive as well but it can be done:
- Enter the Compaq Deskpro SFF's BIOS by pressing F10 after you power the machine on
- Go to 'Security' > 'Set Power On Password'
- Do your thing and hit F10 to save it
- As soon as you do that a new option 'Password Options' will appear in the 'Security' tab, go in there
- Enable 'Network Server' then hit F10 to save it
- Save changes and exit the BIOS
From now on the machine will not complain about missing keyboard on boot. Alternatively if anyone plugs a keyboard in, it will ask for your password on boot.
Credit goes to this gentleman: http://m0n0.ch/wall/list/showmsg.php?id=137/36