若在BOIS下可以看到光驅，建議先將光驅設置為第一啟動裝置

試試能否啟動。Make sure you DID set it as the first boot device. I had this story. I encountered a strange bios boot squence problem before. A friend suddenly couldn't boot his machine. I was told that the system had multiple hard drives and only one had the OS. I could see all the hard drives shown on the hard drive boot sequence list, and the BIOS indicated that it would check the drives on the list sequentially to boot the machine if an OS was found. Before I would make the conclusion that the OS on his hard drive might be corrupted, I suddenly was hit by the idea to play with the hard drive list a bit, that is, changing the sequence of the list. When I moved one that was on the 3rd position up to the 1st, the machine booted successfully. What a surprise! Obviously, only the 1st HD was checked and others were just simply skipped. (I still didn't know what caused the sequence of the list in the bios to be changed in the first place, though)

If it still couldn't boot from 光驅, then as 充數 suggested, replace the 光驅。It's safer than playing with the HD for your data.