Entering CMOS on Compaq

I am currently in computer school and I am working on a Compaq presario 866. I decided to format my hard drive and install a series of different operating systems to document likenesses and differences about them.Well, anyway,after I formatted the hard drive I re installed the cdrom drivers, but the floppy drive is booting up first and I need my hard drive to boot first in order to pick up my cd rom to install the operating systems. I have tried every key and combination I knew and have been told.
Please, does anyone know how to change the boot sequence on this compaq computer, I can’t get into cmos..
Thank You, Neil Hunt