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
What is BOOTMGR?
from Microsoft's official site to create a bootable USB drive. Method 1: Startup Repair (The Easiest Fix) windows 7 bootmgr download
Causes of Bootmgr Issues in Windows 7