Windows 10: Windows 10 upgrade went OK and ran well for 10 days, then won't boot

Hi, I have high hopes for joining the forum so I hope someone can help me out with this problem: I upgraded to W10 on the 8th August, it was worth the wait, really enjoy better browsing and was getting used to finding my way around W10. about ten days on, I tried to load a piece of specialist software called NAVISWORKS Freedom 2015, perhaps 3 times over before I gave up ! I only mention this because a few days later (when I had forgotton about NAVISWORKS), my PC failed to boot into windows. I looked into BIOS and my 3 disks were there, but my main disk with W10 installed(on 1 of 3 partitions) was no longer booting. Eventually I found that if I changed boot priority (which I can only elect for diagnosis on an ad hoc basis and not permanently in my bios) to another of my hard disks, W10 booted up and runs fine, except when I shut down/restart, it won't boot again.
So I in the situation where if I leave the PC in sleep mode when I would otherwise ordinarily switch off it's OK, this is of course not practical soo I am trying to fathom what's going on.
I have tried W10 diagnostics - of course Windows self fix is as usual pretty much useless so no luck there, it just tells me I've got to reload, either at huge inconvenience or at slightly less inconvenience! So I really don't want to do that.
I have also been mooching around at the command prompt options trying to understand Bootsect.exe functionality to see if I can tell Windows to look in the right places for boot info, or reinstate boot info I may have somehow inadvertently trashed.

I have attached a screen shot of my Disc Information which shows my 2 relevant disks, 1 and 2 with their partitions. Prior to W10 update, my W7 OS was in and booting from Disc 2 (C): after W10 installation the new OS was in and booting happily from the same place. Now, whilst W10 is still located in Disc 2 (C): it won't boot, but if I select the F12 option at startup and instead boot from disc 1 (not sure whether from D,G or H) it boots up, perhaps taking a little longer to get up and run than I recall of my early days of W10 performance.

From my limited understanding, it seems as though something I or perhaps my abortive attempts of loading NAVISWORKS have done has rendered my system blind to the new W10 OS for the original boot drive, but what I don't understand is why it is possible to boot from a different drive, is it a matter of re pointing boot commands at the correct drive, or reinstating a "label" identifying the OS Drive ?

None of the diagnostics I have run had indicated any hardware problems.

Can the forum help with my challenge to avoid the dreaded option of a clean r-install :-(

May Thanks in anticipation

:)

 

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i upgraded to windows 10 from 7 everything went ok till next day i turned desktop on no boot up only red light on desktop nothing at monitor put boot disk in won't can't read from dvd drive no sound nothing asked microsoft tried doing what they told
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