When you power-on the computer, keep pressing the appropriate (F2?) key that will let you into the 'Boot menu' - from this menu, select 'hard disk' as the 1st boot device in the boot sequence, and exit. If everything else is ok, the computer will boot up.
If you want to boot from the 'recovery CD', then select the appropriate DVD drive as the 1st boot device in the boot sequence. Proceed from here.
After you finish doing what you intended to do, don't forget to reset the boot sequence to boot from the hard disk as the 1st boot device.