For anybody that's wondering out there, Pro Tools 8 works with Windows 10. At least it did for me.
Pro Tools has always been very fussy, so I was very leary of trying the upgrade, but I finally gave it a shot. I have Pro Tools 8.0.5 (yeah, I know that's super old), and I installed Windows 10 Pro 64-bit over Windows 7 Pro 64-bit.
It took Pro Tools what seemed a longer time than it used to to load, but it did load, and played back without issue.