Is this an ex-company/school machine, where did you get it? L
For Compaq you should repeatedly tap the F10 key while the system is booting, that should get you into the BIOS and PW screen if one is needed. However, unless I am misreading your question, the boot order is contained in the OS, not the BIOS. Only the boot device order is controlled in the BIOS.
What happens when you try to get to the BIOS? If the problem is that you don't have the BIOS password, a factory-trained service technician MAY be able to reset the BIOS to its original configuration without a password. They don't publish instructions for this, since in general if you don't have the BIOS password you aren't the machine's owner and have no business accessing the BIOS configuration.