Dual Boot issue with NVMe

[spnorton]

Building a new PC and want to dual boot Win7 and Win10. Using an X299 MB and Samsung 960 NVM3 drive. All installs from USB devices with UEFI.

I successfully installed Win7 after I figured out I'd need a Samsung driver to support the 960.
Then I successfully installed Win10 on a second partition on the drive, and it didn't happen to want the Samsung driver, but no matter, it still worked.

THEN... I tried booting back into Win7 and it failed. Blue screen of death. I've run into this issue before on other builds and somehow have always been able to fix via repair... but NOT this time. At least one of the messages said that my GPT partitions weren't in the right order. Ugh.

SO... I decided to blow everything away and this time start with new partitions and install Win10 FIRST. This time it wanted the Samsung driver, but it all installed correctly. So far so good.
Now I attempt to install Win7 and can't do it to save my life. It has a hard time finding the Samsung driver, and when I finally got it to see it, it kept insisting driver wasn't appropriate for any drive hardware on the system. I also tried installing Win7 from inside Win10, and that didn't work either, first saying it couldn't create the required partitions and I should boot from the Win7 instead. I also tried first creating the required partition first from inside Win10, but that didn't work either.

I'm at a loss... Willing to blow everything away AGAIN if someone can suggest a "best practice" to get this done. help!

 

[spnorton]

Okay, I've solved my problem... I found my original Windows7 CD and installed from that. I put the NVMe driver on another CD (I have 2 CD/DVD drives in this build) and the install accepted the driver, and found the NVMe drive and installed on the partition I wanted. Dual booting into Win7 or Win10 is now working! Still not clear to me why installing from USB would act differently...

Still unsure why I didn't get more messages of GPT partition "out of order" but I'm not going to overthink that one.

The only other possible clue to my original failure because of installing Win7 before Win10, might have to do with the hidden partitions created with the 2 OS installs. Win7 creates 2 hidden partitions of 100M and 128M. When I installed Win10 first, it created 2 partitions of 100M and 450M in sizes. I wonder if the initial small sizes of the Win7 install weren't large enough to also hold the Win10 boot/partition info, and maybe it "stole" some required info from the Win7 partition causing the Win7 boot failure? I don't know that answer, but I'm likely to run into the same problem when I try and add a Win10 partition on my laptop... I'll probably have to perform a "new" install with Win10 first like this...