This error is generated by the computer's BIOS when the boot sector or master boot record of the boot drive is damaged or missing. This error can also occur if the boot device has been improperly configured in the BIOS. In this case, data in the partition may be valid and undamaged, but there is no bootable partition.
NOTE: This message also occurs when a non-bootable disk is left in drive A during startup. If you receive this error, make sure that there is no disk in drive A and restart your computer.