Dual Boot -deleting Files on Win 7

Hi
What I have
HDD Win 7 Home Premium Activated
SSD Win 10 (Upgraded Win 7) Activated
Dont have a Boot Manager
Can choose Boot up Disk from BIOS at startup
If I choose Win 10 - All Boots Well, No problem
When I choose Win 7 after using Win 10
Chkdsk runs and deletes thousands of Files
Finishes chkdsk and Boots Win 7 fine
Win 7 Boot after Win 7 Boot - no chkdsk and Boots fine
I think it might be making changes to make it the C Drive - but thats without knowledge
both Win 10 and Win 7 use C drive
When installing Win 7 before the Upgrade, I installed to "unalocated" space
which I read would give it a C Drive
as alternative to Creating into a Drive Letter eg G Drive
I could live with it as it is, if it were not for the Long Startup deleting etc to Win 7 - it also has my heart in my mouth that sooner or later the deleting would malfunction
I would really appreciate some Help, I am at a standstill and dont want to tinker and screw everything up and apologise for the ameteur descriptions
I am sure you might want some more info, but not sure what
in anticipation
Thanks

Turn off fast startup in Windows 10:
Fast Startup - Turn On or Off in Windows 10 - Windows 10 Forums

Also, in your situation, it would be a bad idea to allow sleep or hibernate in any of your power settings.

Thanks
I will Report back tmrw with Results which look so logical I am sure will be good
either way, Thanks til tmrw
I cant do now

I am so grateful for the reply

I have a similar setup and experience to yours.
I did a free W7 to w10 upgrade on a dual boot W7 OS.
The upgrade installed without errors, everything looked good, i thought cool...
I attached the other W7 disk and booted with that OS.

It had to run a disk-check and found thousands of errors on the "W10 upgraded" disk.
Fought with it for hours tying to get both OS's working reliably.
Finally gave up and did a clean install of W10 x64 over the W10 x86 upgrade install.
That fixed all my problems for both OS's.

I've always done a clean install when going to a new OS (version).
I wanted to try an "OS update".
It just didn't work well for me, the clean install did, and does.

Consider a clean install, but you will lose all installed programs, settings, etc.

Thanks NavyLCDR - your experience and Knowledge saved me hair - Thanks
I did as you said and Turned Off Fastboot in Win 10
used instructions in the link you provided above
worked a Dream
also Turned Off Hibernating, Sleep and Hybrid Sleep in Win 7

DavidE suggests a Clean Install of Win 10, which wouldn't be too much hassle if it gave Benefits
as everything else is working well as far as I can see, but if it would allow me to Sleep or Hibernate, it would be a Benefit, I think

DavidE, Thank you also your Help

Both, please reply if you think there is something else I should do, or would be better done
Great People on a Great Forum

Sleep or hibernate should only be a problem if the computer goes to sleep or hibernate in Windows 10 and then you restart it in Windows 7. Fast Startup in Windows 10 is basically a deep form of sleep - somewhere between sleep and hibernate.

You could try this on your Windows 10:
Repair Install Windows 10 with an In-place Upgrade - Windows 10 Forums

You won't lose anything but time - in theory.