Windows 10: Dual boot Win10 and Win 7. Win 10 Hijacks win 7, and won't play nice.

Hi and good morning. I am a noob with Win 10, and am doing what I can to figure it out.
So here's the skinny. Win 7 is the default on Drive C. Win 10 is on Drive D.
When I boot into win10, it automatically renames the D drive to C and makes itself the default.
So after a few hours of using 10, to switch back to win 7, I have to reset the boot because win 10 tries to come up first even though it is not default.
This is excruciatingly annoying. The only reason I have Win 10 is because of An Occulus Rift I got for Christmas!
(My wife really Loves me...or not)
Otherwise I would happily Fallout on win 7.
I searched in vain trying to fix this dilemma.
Any advice or direction would be appreciated.
Thanks

:)

 

Dual-boot Win10/7 or go back to Win 7

This^^

I only use, or recommend, dual boot if a new/separate HD is out of the question. Way less hassle and potential problems.

 

Dual-boot Win10/7 or go back to Win 7

Separate Hard Drive for win 7 and win 10
select boot drive at bios when Booting ( F10 )
Keeps them entirely separate and makes wipeing disk later easier

 

Dual-boot Win10/7 or go back to Win 7

That's as I thought hence my thinking dual boot or simply go back to 7.

I only have an SSD (OS) and 1TB HDD which is my Steam/downloads drive.