Final answer:
To determine if the boot disk is at fault when a computer does not complete its boot sequence, check the BIOS boot order, repair the MBR via Windows Recovery Environment, or test the disk with diagnostic tools or in another computer.
Step-by-step explanation:
If a computer is not completing its boot sequence and the Master Boot Record (MBR) is suspected to be the issue, there are a few steps that can be taken to troubleshoot the problem. First, enter the BIOS settings to ensure that the boot order is correctly set with the C drive (where the MBR is located) as the primary boot device. If the boot order is correct, you can attempt to repair the MBR using tools such as the Windows Recovery Environment (WinRE). This can be accessed by booting from a Windows installation media and navigating to the 'Repair your computer' option. In the WinRE, you can choose 'Troubleshoot' and then 'Command Prompt' to use command-line tools like bootrec.exe to attempt to fix the MBR. If these steps fail, it might indicate a hardware issue with the disk, in which case you may want to test the disk in another computer or use disk diagnostic tools to check for disk errors.