You might need to download or repair Bootmgr in the following situations:
A: Upgrades can leave old boot fragments behind. In that case, perform a clean "bootrec" rebuild (Method 3) and manually delete the old bootmgr from the Vista era. windows 7 bootmgr download
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 You might need to download or repair Bootmgr