CompaqProlinea 590 & BIOS

Hi guys, I have this ancient machine and I want to boot from the CD-Rom drive, the only trouble is I don’t quite know how to get to the bios because it just isn’t the ususal commands used to get to the BIOS (DEL_Key or F2).
Also I have been to the manufacturer’s web page and they do not seem to have any help whatsoever on this subject. Anyone who can help on this I would really appreciate.

Thanks a lot.