Insert your Windows Server 2012 R2 installation media (DVD or bootable USB) into the server and restart it.
Boot into the Windows Recovery Environment (WinRE) using your installation media, as described in Phase 1. Select > Advanced Options . Click Startup Repair . windows server 2012 r2 boot repair
If the bootloader is fine but files are corrupted, use these integrity tools: sfc /scannow /offbootdir=C:\ /offwindir=C:\windows with your actual OS drive letter). DISM Cleanup: dism /image:C:\ /cleanup-image /restorehealth Microsoft Learn Step 5: UEFI/GPT Specific Repair For servers using instead of BIOS: to find the EFI partition. Select that volume ( ) and assign it a letter ( assign letter=S Exit Diskpart and run: bcdboot C:\windows /s S: /f UEFI is the OS and is the EFI partition). Insert your Windows Server 2012 R2 installation media