Dual Boot Win10/7 problem - Win10 SSD no longer bootable after Windows Boot Manager and CHKDSK issue

fenns_treasure

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Apr 24, 2018
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Dual boot problem - After installing Win7 on separate HD, CHKDSK ran and Windows Boot Manager got installed on my Win10 SSD and now it's not recognized as a bootable device.

Very long post, but lots of detail so you can hopefully help me.

I have Win 10 installed on SSD, with most of my files stored a separate 4TB HDD. I installed Win7 on a third 1TB HDD, and tried to create a Win10/7 dual boot. I failed, and ultimately did something to my Win10 SSD. It is no longer recognized as a bootable device.

I would like help doing three things, and any help is very much appreciated.
1) Recovering my Win10 SSD as a bootable drive.
2) Reinstalling a Win10/7 dual boot the correct way, and figuring out how to share my primary storage HDD between the two OS.
3) If there is no way to easily and safely share the Primary Storage HDD between both Win10 and Win 7 (and without screwing up the OS not in use), I would settle for just having a dual boot option where Win7 runs on its own and leaves the other drives alone.



Here are the steps I took, and what happened:

I already had Win 10 Education on a 500 GB SSD (GTP), and a 4TB HDD for storage (named Primary HDD) (GTP). Then, I installed Win 7 Ultimate on a third HDD, with no other drives connected. This turned out to be MBR partitioned. Then, I connected my storage drive, Primary HDD, and booted up the Win7 OS again. The new OS install didn’t like this and a black DOS screen came on with an error, and did some kind of CHKDSK scan. Then the Win7 OS loaded, and I could see all of the files in the Primary HDD.

Next, I turned the comp off, connected the Win10 SSD, and booted it up. So now all three drives are connected. I was expecting windows to ask me to choose an operating system, but it never did . The black DOS screen came on again, did the same error and filecheck again, then Win7 booted up, not Win10. In Win7 I was able to see the SSD where my Win10 was installed, and access the SSD folders. I restarted the comp and went into the BIOS to check boot orders, my SSD was listed differently.


The BIOS used to have an entry listed as Samsung SD 850 EVO. Now the listing showed: Windows Boot Manager (Samsung SD 850 EVO). What does that mean?
B5f2ycr.png


I tried to simply move this entry to Option #1, but it still loaded to Win7. Then, I went into “Hard Drive Boot Priorities” and saw the correct listing for Samsung SSD 850, and made it Boot Option #1.
Lg1QuGv.png


Then tried to reboot with this listing as the first boot priority, and took the WD drive option out entirely.
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It still loaded to Win 7.


I loaded up the Win7 OS again, and Disk Manager shows this:
5BVx3jK.png


When I connect only the Win10 SSD I get a black screen saying I don’t have a bootable device.

I assume the CHKDSK scan was because Win10 and 7 filesystems don’t like one another, and the new Win7 OS screwed up the boot record on the SSD, when it tried to “fix” the Win10 files it didn’t recognize…or something like that. Assuming this is true, how do you get a dual boot to work and not have the CHKDSK scan happen anytime both OS are recognized during the BOOT sequence. I read some posts about installing Win10 after Win7, but I don’t see the point in that. First, I installed both OS independent of the other, and then connected the drives. All the drives are connected to the mobo all the time, so there isn’t any “first” install anyway.

Any thoughts on how to recover my Win10 SSD as a bootable drive? Any thoughts on how to set up a dual boot that will work? Before I tried the dual boot I read several forums and posts, and I saw conflicting information. Some threads said you had to install 7 first, some said just install them separately, and it wouldn’t matter. I installed separate OS on separate drives, independently. Obviously something went wrong because it caused a CHKDSK scan each time I connected a new drive. I can keep reading posts on how to fix it, but I see conflicting opinions on dual boot processes and it seems wise to ask for help before I make this situation worse. Tell me I didn’t ruin my Win10 OS install.

All three of these drives will always be connected the mobo, so I need to make sure the acting OS is not doing something negative to affect the files in the HD with the other OS.
 
Solution
The confusion there is because of different boot modes being used.
Windows 10 is installed in UEFI mode, windows 7 is installed in legacy/csm boot mode.

Boot entry called "Windows Boot Manager" is for UEFI boot - you can boot windows 10 with that.
You cant boot windows 10 with boot entry "Samsung 850 Evo" (legacy/csm boot entry), your SSD doesn't have necessary partitioning and bootloader for that.

What you have to do to achieve DUAL boot is - you have to add windows 7 boot entry to windows 10 bootloader.
Make sure windows 7 is 64bit version. With 32bit version this will not work.
1. Boot into windows 7 with all drives connected (legacy boot option - 1TB HDD).
2. Assign drive letter to 100MB EFI system partition on SSD (letter X: for...
Get easyBCD,there is a free community version that's all you need,and run it on windows 7 that's still booting, it will alow you to write a bootblock to the win10ssd (deploy bcd->write mbr) if you want the boot menu to be on that win10 ssd then also install bcd on the first partition of the ssd.
Then go to file->select bcd store to load in the bcd from the ssd,on the tab add new entry you can easily add both windows to the menu.

Booting works by first looking at bios settings so make sure bios is set up to look first at the disk you want it to see first (win 10 ssd) you shuffled the disks around that's why you got the flashing cursor,it appears when bios has no idea where to boot from.
So you could skip some steps and just add new entry and add windows 10 to the menu.

Both windows should be seeing the 4Tb drive,but depending on your mobo it might need a 3Tb+ fix which should be on their download page,3Tb is a hardware limit and I guess you tried to use the drive before running the fix.
 
The confusion there is because of different boot modes being used.
Windows 10 is installed in UEFI mode, windows 7 is installed in legacy/csm boot mode.

Boot entry called "Windows Boot Manager" is for UEFI boot - you can boot windows 10 with that.
You cant boot windows 10 with boot entry "Samsung 850 Evo" (legacy/csm boot entry), your SSD doesn't have necessary partitioning and bootloader for that.

What you have to do to achieve DUAL boot is - you have to add windows 7 boot entry to windows 10 bootloader.
Make sure windows 7 is 64bit version. With 32bit version this will not work.
1. Boot into windows 7 with all drives connected (legacy boot option - 1TB HDD).
2. Assign drive letter to 100MB EFI system partition on SSD (letter X: for example). Execute from elevated command prompt.
  • diskpart
    list disk
    select disk 1
    (1 - number of SSD)
    list partition
    select partition y
    (y - number of 100 EFI System partition, could be 2 or 3)
    assign letter=x
    exit
3. Add windows 7 boot entry to windows 10 bootloader. Execute from elevated command prompt.
  • bcdboot c:\windows /s x:
4. Reboot your pc and make Windows boot manager first in boot options.
5. Also disable fast boot in BIOS options. If you don't do this, it will cause data corruption.
6. Done. Next time you boot your pc, you'll be able to choose either windows 7 or windows 10 to boot in.
 
Solution

fenns_treasure

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Apr 24, 2018
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4,510
Thank you so much for your answers!

I was gone a few days for business, so I couldn't try them out until last night. Following these posts I was able to get my Win10 back and get the Win7 boot entry loaded onto the Win10 bootloader. For some reason I never did get the dual boot option to display on reboot, but I ended up just using easyBCD and it's works great. If anyone thinks easyBCD is not a good idea, please let me know, but it works well for me and was really easy to set up. Of course I am using two Windows OS in my dual boot, so it's pretty straight forward. When I want to run Ubuntu I just use a VM. If I ever decided to dual boot with Linux, I may have to find a different solution than easyBCD.

Again, thank you both TerryLaze and SkyNetRising for the time and expertise, and in how incredibly fast you answered.

Fenn