The BIOS loads the MBR from the active hard drive partition.
This guide provides the necessary steps to fix the "BOOTMGR is missing" error in Windows 7, which occurs when the boot manager file is damaged or deleted. How to Fix "BOOTMGR is Missing" in Windows 7 windows 7 bootmgr download
The area of your hard drive that tells the PC how to load Windows is corrupted. The BIOS loads the MBR from the active hard drive partition
Restart your PC and repeatedly press the setup key (usually , F10 , or Del ). or Del ).