Sorry I am being dense but I didn't follow most of that - both installations were on MBR format disks.
I currently have 6 hard disks in my system plus an SSD drive (Disk 0 - still labelled Win7ProSSD because I never got round to changing the label to Windows 10)
They are all MBR disks apart from Disk 5 - which is a 3Tb data GPT drive
The system currently books from disk 1 (which was the first drive to have windows installed on it when I built the original system.
The System Reserved folder on disk 1 has a BOOT folder and bootmgr system file
During all the recent messing about I set the Windows 7 (C:) partition active and that now too has a BOOT folder and bootmgr system file
Should I set the System reserved partition as the active partition and remove the extra boot info from C:
Also at some point M: (which is on the GPT drive) also acquired a BOOT/bootmgr setup - I don't know when this happened as the drive was added to the system after the SSD but before I upgraded to Windows 10 on the SSD.
I presume the boot config appeared on M: when I upgraded to Windows 10 but was unaware that had happened.
I am not really that familiar with disk formats and the boot process - how can I best recover the boot system to make Windows 7 on C: the only boot option (which it currently is) using the original boot process - and can I then delete the extra BOOT/bootmgr bits on the other drives.
If at that point I start installing a freshly downloaded Windows 10 onto the formatted/SSD what effect will that have on boot processes?