The Master Boot Record (MBR) is a file that tells your computer where to find Windows and from which drive to boot. If it is corrupted, your computer will not successfully start up. You may receive an error message like "Operating System Not Found" or "Invalid Partition Table."If you have already attempted a System Restore, booting into Safe Mode, or going back to a previous build, without success, the issue could be a corrupt MBR. Fortunately, the MBR can be repaired.If your MBR has been corrupted, follow these steps to fix it:1. Access the Windows Recovery Environment: a. Your computer may enter the recovery environment on its own. If you see “Preparing Automatic Repair” allow the system to proceed. b. If Windows attempts to boot normally, you will have to interrupt startup by holding the power button until the computer shuts off. Repeat until you see “Preparing Automatic Repair.” c. By using Recovery Media i. Boot from your recovery media by changing the boot priority in BIOS or selecting the correct boot option from the boot menu. ii. Select your language and keyboard layout – for most users, this will be English US.2. When you see a blue screen with the title “Automatic Repair” select Advanced Options. 3. Select Troubleshoot. 4. Select Advanced Options. 5. Click the option for Command Prompt. 6. From the command prompt, enter the following command:bootrec.exe /fixmbrNote: There is a space between bootrec.exe and /fixmbr7. If you see “The operation completed successfully” you are done.8. Shutdown the computer and attempt to power back on like normal.