Software & Apps Windows How to Write a New Partition Boot Sector in Windows Use the BOOTREC Command to Fix Issues With the Partition Boot Sector by Tim Fisher General Manager, VP, Lifewire.com Tim Fisher has 30+ years' professional technology support experience. He writes troubleshooting content and is the General Manager of Lifewire. our editorial process Facebook Twitter LinkedIn Tim Fisher Updated on January 17, 2020 Windows The Ultimate Laptop Buying Guide Tweet Share Email If the partition boot sector becomes corrupted or misconfigured in some way, Windows will not be able to start properly, prompting an error like BOOTMGR is Missing very early in the boot process. The solution to a damaged partition boot sector is to overwrite it with a new, properly configured one using the bootrec command, a relatively easy process that anyone can do. The following instructions apply only to Windows 10, Windows 8, Windows 7, and Windows Vista. Boot sector issues also occur in Windows XP but the solution involves a different process. How to Write a New Partition Boot Sector in Windows 10, 8, 7 or Vista Start Advanced Startup Options (Windows 10 & 8) or System Recovery Options (Windows 7 & Vista). Open Command Prompt. The Command Prompt available from the Advanced Startup Options and System Recovery Options menus is similar to the one available from within Windows and works very similarly between operating systems. At the prompt, type the bootrec command as shown below and then press Enter. The bootrec command will write a new partition boot sector to the current system partition. Any configuration or corruption issues with the partition boot sector that might have existed are now corrected. You should see the following message at the command line: The operation completed successfully. Restart your computer with Ctrl-Alt-Del or manually via the reset or power button. Depending on how you started Advanced Startup Options or System Recovery Options, you may need to remove a disc or flash drive before restarting. Assuming that a partition boot sector issue was the only problem, Windows should start normally now. If not, continue to troubleshoot whatever specific issue you're seeing that's preventing Windows from booting normally.