Check the boot order in the Bios to make sure that it is correct. Hard disk drive, CD/DVD drive and Floppy if used. The hard drive, IMHO, should always be first boot device.
If available, set the PXE (Network Boot) to disabled.
Check cable connections (reseat),
Check jumpers on hard drive for Master/Slave or Cable Select settings. CS should be avoided unless using a CS cable.
Do not have both HD & CD/DVD on the same IDE cable.
When booting, continually tap the F8 key, this should invoke the Boot Menu so as to boot to CD/DVD.
And lastly, have your BIOS rescan your HD, or, reset your BIOS to defaults.
I take it as read that you are using IDE drives throughout.
have fun! good luck!