At Command Prompt you need to run the FIX BOOT command. As the boot sector is corrupt or damaged.
Try the above and try FIX MBR if the above do not work. on the Hard Drive there is small we can call it a file, this can be replaced if the one at the front of the drive gets damaged as above with the good one from the back of the drive, by running one of the commands above. you may be able to run this from a prompt after tapping F8 as PC is starting, it may be in the list of ways to start-up