Stuck in automatic repair; startup options not working

I was called to fix a PC from the other department. It's stuck with preparing automatic repair. Here's what I tried so far:
1.Tried selecting enable safe mode but after pressing #4 on keyboard, it just restarts and loop again.
2. Tried system restore. it shows rstrui.exe error.
3. command prompt to disable recoveryenabled - no changes
4. command prompt and ran chkdsk /f /r /x C: - done; still looping
5. diskpart listed all volumes to be NTFS. no RAW. - tried bootrec /fixmbr ...
6. Inserted windows 8.1 installation disc
6.1 boot priority shows: HDD, DVD containing win8.1, and another UEFI DVD containing 8.1
6.2 tried different boot priorities
6.3 problem with drive being locked

I'm out of ideas. I'm planning to connect the HDD to other PC's SATA and will act as external drive. What can i do with the files inside aside from backing them up? I'm suspecting a windows update last friday caused this. Thanks in advance