Windows Server 2012 R2 Boot Repair Link

~30% – but when it works, you're done in 5 minutes.

From Command Prompt (recovery environment): windows server 2012 r2 boot repair

Startup Repair scans for missing/corrupt boot files, registry damage, and driver issues, then attempts auto-fix. ~30% – but when it works, you're done in 5 minutes

bootsect /nt60 sys /mbr Then retry /fixboot . If /rebuildbcd doesn't find any OS, rename the old BCD and create a new one: ~30% – but when it works