Why does it say boot device not found?

The message you're seeing is from the system BIOS (Basic I/O System) firmware that is loaded when the system powers on. That firmware maintains a list of bootable devices in your system and goes through that list in order trying to boot each of the devices it knows about. If it's checked all of them and can't find one that will boot, you get that message.

Unfortunately, there are a lot of reasons why the BIOS might not find a boot device. Off the top of my head and in no particular order, here are some of the reasons for that.

• CMOS battery has failed so BIOS has forgotten it's list of bootable devices.
• Hard drive has failed and can't be read.
• Boot record on hard drive has been corrupted and can't be loaded.
• Assuming you're running Windows, some of the files needed to load the operating system are missing or corrupted.
• Cable connecting the hard drive to the motherboard has failed or come loose.
• Power to the hard drive is broken or disconnected.

Diagnosing this problem may take a while depending on how much expertise you have with Windows and BIOS, but we can try to step you through some of it if you want.