How to boot from HD

I needed to reinstall Window, so I boot up my old HP computer and hit the DEL key to change the boot menu to boot from CD (and foolishly remove the boot from hard drive). Now that Windows is installed, I can’t change the Bios configuration because every time the computer boot up it asks me to hit any key to boot from CD so I can’t change the Bios menu anymore by hitting the DEL key. Any idea how I can switch the boot from CD to HD ?