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Windows 10 update screwed dual boot system - STUMPED!!

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Carol Haynes:
Should the windows partition be set to an active partition or should it be the small system partition set to active?

ajlixx:
it is probably another problem - creators update contains small cmd based applet called mbr2gpt, which convert mbr disk to gpt disk without files loss - i have read that it should be used through cmd, but i met on other forums at least 1 case where, it seems, it got at work automatically and tried to convert disk to gpt - it is especially provided for 7 to 10 upgrade cases, because 7 doesnt serve fully uefi

if it is your case you should ascertain what is exactly partition style on yor booting disk, i mean disk set in uefi\bios as booting - you could do it for example with partition wizard bootable cd started from cd - if it is gpt style there will be small 100mb partition efi on disk formatted in fat32 - and then use system applet bcdboot to write bootloader files to this partition (or just from 7 installer cd, using diskpart commands list disk, etc)

dual boot system is in this case of no consequence - you should be always able to add other 7 to bcd in case of problems

what partition should be active - of course with folder boot and bootmgr file - in partition wizard you can check folders\files on partition - just to mark partition and choose explore partition in menu - but only on mbr disk of course; system partition 100mb on mbr will be formatted in ntfs, not fat32

in gpt style disk there is no active partition - instead is system partition efi (esp - efi system partition), with windows boot manager files

sorry for my english, but i am in great hurry!

eventuallly, if you can use bcdboot, from installer cd or from recovery partition\folder, if possible (or from system, is in system32) - command something like

bcdboot c:\windows /s x: /f uefi

/s x: means

system partition letter = x: - you should assign letter to efi for example in diskpart, or in partition wizard, because normally this partition is without letter - letter is of no consequence for functioning because partition is recognized by uefi by guid in gpt partition table, not letter, letter is only for bcdboot to identify it; x of course only example

or maybe there are other commands in bcdboot automatically recognizing system partition efi without letter - i am no expert in bcdboot

another possibility - you should make functional 7 on hdd, and repair start on ssd from this 7, for example using easy bcd - easy bcd could repair both mbr and gpt start

to make funcional 7 on hdd you should mark partiton as active in diskpart, write codes on start sector of disk and active partiton (from cd - commands bootrec /fixmbr, and /fixboot), and write bootloader to active partition, command in bcdboot in 7 (all this with detached ssd)

bcdboot c:\windows /s c: /f mbr

to write bootloader bcdboot uses boot files templates from system registry folder, so you would not have systems choice in 10 - you should add both 7 to new bootloader in easy bcd

on hdd you can have mbr style, only on booting ssd gpt\uefi - partition style on data disk is of no consequence

to use bcdboot is probably important, because there are slight differences in bcd file for mbr and gpt; but easy bcd also can write right bcd

Carol Haynes:
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)

Windows 10 update screwed dual boot system - STUMPED!!

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?

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