Adding Windows 7 dual boot to existing Windows 10 install on same SSD?

[bledd]

What's the best way to do this?

I'm not a fan of dual booting but Company of Heroes performance is almost twice as good in W7.

 

[marc2003]

With all my previous dual boots, I always ran setup for the 2nd OS from within the original OS desktop. That always works with oldest OS first but I can't say for certain it would work "backwards". You might want to test on a VM or spare hard drive first.

edit: just to clarify one other thing - don't run setup.exe from the root of the ISO/DVD. Use sources\setup.exe

another very late edit: I'm sure you already know you'd have find room for another partition, create and format it using disk management. Just mentioning it for anyone else who might read.