My computer has Windows 8. My BIOS settings allow booting from optical drives and external drives. However, if I have Windows XP on a DVD or a USB flash drive (or USB hard drive) I get an error message:
"Operating system not found". This also happens if I make a rescue CD and try to use it when the computer is rebooting. Otherwise the USB ports are working fine.
I would appreciate any advice about how to solve this problem.
Have you access to another PC to check your XP CD and rescue CD are working (bootable) ?
(XP usually comes on a CD not DVD)
I suspect your DVD drive may be faulty or some bios or hardware setting is preventing it booting up on the DVD drive though presumably you created the rescue CD in the DVD drive.
If this is a Desktop PC you should be able to check which sata port the DVD drive is plugged into and look up the motherboard user guide for any special instructions (such not using certain ports for DVD's or only using certain ports for hard disks)
(user guide is usually a PDF on driver disk or manufacturers web site. years ago it would be printed on paper !)
Is this a new PC you bought with Win 8 or an old PC you updated to win 8 ?
If this is a new PC ask the supplier or manufacturer.
If you have a newer machine that has Windows 8 running, you may have a UEFI BIOS that supports secure boot. If you want to boot a legacy OS you will need to turn off that feature or the BIOS will block boot process. I think only windows 8 currently uses the new secure boot option. Windows 7, vista, xp, ... need to have secure boot turned off. (will not hurt booting windows 8 either)