I need to tell you that Win7 doesn't have Hyper-V
You can run Virtual PC on Win7, but I wouldn't. It's far less powerful virtualization, plus I'm not all that familiar with it.
This is good, planning is important.
I know the feeling about using your 8.1 machine - it took me a while (4 months) to setup a Hyper-V machine on my newly upgraded laptop. It was my only machine at the time.
I think you'll have much better luck using the Win8.1 machine ... more than that though, it's the only one I can really help you with because it has Hyper-V.
I can point you to a Virtual PC tutorial, but I'd have to read it and scratch my head while you read it and scratched your head - no sense both of us doing that.
Set p the Hyper-V machine all the way up to installing Win10. You won't be able to do anything with it until an OS is installed, but the practice might give you the confidence to move forward.
Let me know if you decide to use the 8.1 desktop or even just test setting up a Hyper-V machine.
It's pretty easy and very safe - everything you'll use is native to Windows.