I can't tell what CD you tried to boot from. Also, it is well known that after just a few years that the CD drives tend to lose their capability to boot. To fix that is easy, you replace the failed CD drive.
I have a Sony Vaio VGN-FS790. About a year ago the hard drive crashed beyond repair. I just bought a new hard drive and installed it without a problem. The computer now starts and displays the "Operating system not found" message. I've tried pressing <esc>,<f2> to enter the BIOS and booting from the Optical Drive but the system simply goes back to the "Operating System not found" message.
In the BIOS there are the options to boot via Optical Drive, Floppy Disk Drive (which I don't have), Hard Disk Drive and Network.
Can anyone please advise me on what to do now?