How many optical drives are fitted to this machine? If two or more check that the disk you want to boot from is shown in the drive in the 'Computer' Window (assuming a Windows OS). Then note the drive letter of that drive and make sure that's the drive you're selecting to boot from in the BIOS.
Is it a UEFI BIOS or an Award-type setup? When you select the drive device are you saving the BIOS settings before re-booting? (hit F10 and Enter).
What disk are you trying to boot from? Is it a bootable disk? If it's a Windows OS disk does a window open for it within an existing Windows installation when you insert it? Is it a genuine Windows disk or an iffy one?
The problem is either:
a) Wrong drive selected in BIOS
b) BIOS settings not saved on exit
c) Faulty optical drive or cable
d) Faulty or counterfeit boot disk
With that as a guide a process of elimination may give you a result.
However, as you seem to have experienced a great deal of problems with your current setup it's a possibility something major may be amiss.