Recovery from external drive boot?

[therealex]

I found Visual BCD after repeatedly having this issue:

My windows 10 system would suddenly shut down - instantly, no normal shutdown.  After that, I couldn't boot from my C drive.  Using either Hiren's or the Windows 10 install, I would try bootrec but get responses like "access is denied".  I then went through the whole complex method of creating a new partition, running from that (didn't work), etc.  The first time this happened, I had just finished a backup three days before, so I swapped drives and restored the missing files.  This last time, I got it working but upon running Bcdedit it gave me all kinds of error messages.

So I d/l Visual BCD, ran automatic repair - BOOM!  It all worked. Now Bcdedit gives me the proper response.  So (finally) my question:

If this happens again, can I run Visual BCD from, for example, Hiren's 64 bit?  Will it fix what would be considered an OS on a different drive?  I know I can specify a source, but I'm not sure if that's what I would need to do.  BTW - I made a backup store and put it in my root on the C: drive.

Thanks for your help.

- Russ