Something on my windows 7 partition prevents win10 upgrade or boot

So I have gone through all the usual hoops I can find on the upgrade issues, mostly based off the one error I have managed to get spit back: 0xC1900101 - 0x20017

This is usually found to be a driver error, but after removing everything possible to no avail I said screw it and went for the clean install.

The install media would get stuck at the spinning dots even after booting directly to it, that is until I removed the older hard drives, namely the one with my win7 install. I now have a clean win10 sitting pretty (on an SSD), but here goes my issue, if I plug the win7 drive back in (with computer off) I get stuck on spinning dots again! After restart I can get a repair screen which only leads to a black screen with a mouse. Take out the one drive again and I can get in. Fun stuff so far.

What is most curious: I dropped in the drive when win10 was up (yay sata hotswap), and it read the other two partitions great! But the win7 partition isn't read, leading me to believe something is corrupted there.

Ultimately and ideally I would like to do an upgrade to keep my files around and not deal with restoring everything. less ideally would be getting the win10 install to see the win7 install partition, but I would bet these issues are one in the same.
I have run chkdsk and /sfc scannow, no errors on either.

For record is what I have in win7, and when I hotswap this drive in on 10 C: will not show up.

TIA

Will the computer boot into Windows 7 with only that HDD connected?

Yes, I had attempted the upgrade that way at some point.

If you have the storage available, such as external hard drive or network storage, I would suggest loading Macrium Reflect Free on the Windows 7 and creating an image of the disk. Then you can install Macrium Reflect Free on Windows 10 and mount the image files created and see if you can access the data that way. It would be a start....

Also, a screenshot of the complete disk management window with all the information would help.

I will get macrium and (depending on the time it takes) post back within the hour

I can read the image in macrium. I would still rather upgrade but at least this is workable in the end. Just going to be a pain to configure all the little bits, which seem to transfer fine through upgrade (upgraded another pc), not to mention I will have to format that partition and lose the dual boot (just for convenience)

We can try a few things.....

First - make a Macrium Reflect Rescue USB/DVD and make sure the computer will boot from it into Macrium Reflect.

Then, boot into Windows 10. Turn off fast startup:
Fast Startup - Turn On or Off in Windows 10 - Windows 10 Forums

Shut down the computer by holding the shift key when you click shutdown from the power icon on Windows start menu. (just to make sure you get a complete shutdown, but turning off fast startup should give a complete shutdown anyway).

Reconnect the Windows 7 drive. Make sure the Windows 10 SSD remains selected as the primary boot device in bios and attempt to boot into Windows 10. Turning off fast startup may fix the problem.

If that doesn't work - then reboot the computer from the Macrium Reflect Free rescue USB/DVD and under the restore option is a utility to fix boot/startup problems. Run that utility and see if that fixes it and sets up dual booting.

The rescue USB froze on finding plug and play devices, restarting now to cancel that early

No dice trying to cancel, I could open a cmd but diskpart didn't seem to work.

So, it's back to booting from either the Windows 10 drive by itself, or into Windows 7? You don't have Raid or anything special like that set up in bios? Bios disk controllers should be set to AHCI mode. What disk drive controllers are listed in device manager in Windows?