'NO to powering down (deliberately!).'
Really, even though you have now corrected boot.ini ?
But if that's the case the problem should resolve itself by reconnecting the drive ? If the system can't load into windows, it can't be 'disk manager's fault in that circumstance which leaves the correctly functioning boot.ini.....
I feel that in the spirit of experimentation you should give it a go.
Ah, thanks re multiboot. Used to but don't now. That explains the boot.ini.backup file.