concerns booting from the cd-rom

Hello,

I am trying to boot from the cd-rom and I am getting the message "Cannot boot from CD- code: 5". The PC sees the hard drive and the cd-rom and it is able to boot from the a: drive. In the BIOS the sequence to boot is set at cd-rom, c:,a:. I am able to boot with the XP OS disk but when I try with the win 2K pro disk I get the above mentioned error. HELP!

Thank You.

Alan.