A boot device is any piece of hardware that can read or contains the files required for a computer to start. For example, a hard drive, floppy disk drive, CD-ROM drive, DVD drive, and USB jump drive are all considered bootable devices. However, unless the necessary boot files are stored on the drive, diskette, or disc, the computer will not be able to boot from that device.
The most commonly used boot device or boot drive is the hard drive. When an operating system, such as Microsoft Windows, is installed onto the hard drive, it copies the boot files and drivers required to load Windows onto the computer. When installing a new operating system, troubleshooting the computer, or booting from another drive, such as the CD-ROM drive, a bootable disc or setup disc is inserted into the drive. If the boot sequence is setup correctly in CMOS setup and the bootable disc is in the computer, it will load from the disc instead of the hard drive.
Creating a bootable disc or drive
Today, there are many different ways to create a bootable disc or another type of bootable drive. If you need to create a bootable disc or drive to troubleshoot or install an operating system, follow one of the links below that relates to the bootable media you're trying to create.
If you're trying to install a new operating system, such as Microsoft Windows, the setup disc or USB drive is bootable and can start the install without the aid of another disc or drive.
No boot devices available
If the computer hard drive is not working, has not yet been set up, or there are no other bootable devices, you will receive an error when the computer boots. Common errors in this situation are "no bootable device" or "no boot devices available." This error indicates that the computer looked at all available devices, but did not see any drive with boot files. If the computer was working before getting this error message and no new hardware was added, it's very likely that your hard drive has failed.
However, before assuming the hard drive has failed, make sure no cables (especially USB cables) are connected to the computer. Also, ensure that all diskettes, CDs, and any other USB devices are removed from the computer. In some situations, the computer may be trying to boot from a non-bootable device and causing this error.
If there are no other disks, discs, or USB drives connected to the computer and you've recently moved the computer, open the computer and verify the cables are connected to the hard drive.
If none of the above steps help resolve the problem, unfortunately, it is likely a bad hard drive.
Inaccessible boot device
If the computer has detected a boot device that is not bootable, an error, such as "inaccessible boot device," is shown as the computer boots. When this error occurs, it is an indication of a corrupt boot device or a diskette, disc, or USB drive attached to the computer is not bootable. Remove any diskettes and discs from the computer and disconnect any USB drives, MP3 players, or cameras connected to the computer.