When you turn on a computer, it goes through a sequence of steps before the operating system loads. Any number of errors might display during this time, but the Bootmgr error means that the boot sector is missing or damaged. Some causes include file corruption, corrupt sectors or loose cables. This error also surfaces when your computer attempts to boot from a non-bootable source. There's more than one way to fix it, with varying degrees of success.
The Boot Configuration Data is a database that contains the computer's boot configuration and is presented by the Boot Manager. It's similar to the Boot.ini file used in Windows XP, as it displays menu options at startup, when applicable. Rebuilding the BCD manually is another option for stopping the Bootmgr error. Boot the computer using the Windows disc and choose "Repair Your Computer" from the list of options. From the System Recovery Options, click "Command Prompt" and type "Bootrec.exe" without quotes in the window. Press "Enter" and type the following: "Bootrec /RebuildBcd," minus the quotes.
System Restore is the generic fix for all Windows-related problems. Backups of system files are made often before they're altered -- for example, prior to installing an update or new program. The service allows you to go back in time, restoring your system to the state it was in before problems occurred. It can't fix everything, but there's a good chance your problem will go away after you use it. Reboot the computer from the Windows disc and launch the System Recovery Options dialog box. Click "System Restore" and pick the most recent restore point prior to the error.
Advanced Boot Options
The Advanced Boot Options menu is available only on computers with a recovery option. This is often found on laptops where the operating system is preinstalled and doesn't come with an installation disc. Using this method, you can launch an automatic repair that attempts to fix boot problems. Press "F8" before you see the Windows logo and use the arrow keys to select "Repair Your Computer." From the Recovery Options menu, choose "Startup Repair" and let it run until prompted to restart. It may need to restart multiple times before the repair is complete.
If your computer doesn't have built-in recovery options, you can access them through the Windows Recovery Environment on the installation disc. To start WinRE, place the disc in the drive and press any key when prompted. After selecting your language and input method, click "Next" and then "Repair Your Computer." Choose your drive from the menu and click "Startup Repair." Startup Repair will scan for any problem that would prevent a successful boot and fix it automatically. It also runs the Disc Checker if errors in the file system are found.