How To Fix Windows 8 Master Boot Record

Step 1: Insert the Windows 8 Installation Disc in your system’s optical drive, or use a bootable USB for that matter, and make sure you boot your PC using this removable media.
Step 2: On the Install now screen, select Repair your computer.
Step 3: On the next screen, choose Troubleshoot, followed by Advanced options.
Step 4: From Advanced options, launch a command prompt windows, and enter the following command:

bootrec.exe /fixmbr

Step 5: Once the command is finished, reboot your computer the normal way, and Windows 8 should load just fine now.