Cd drive does not boot

first what is it pc or laptop and access of bios what does it do when you try to access let me now make model then my be able to help

Press either F2 or Del to access Bios on Boot up.
once in Bios check if Drive is connected.

If desktop, and you cannot see CD ROM in BIOS, check jumpers on back of drive. Change to cable select position. (little pin that pulls out at back)

Once you can see in BIOS, it should be plain sailing.

If you had everything working, and just deleted the Primary Partition, make sure you have a DOS partition installed, you can check using something called fdisk from your DOS prompt. If this is OK, then try again to get in to BIOS. (if F2 or Del doesnt work within first 10 seconds of turning machine on( repeatedly hit if your not sure when to press it) try ESC which should remove any splash screen, revealing the key to press)
Once in Bios change your boot sequence to 1CD 2Hdd then boot with your CD ROM