'If' a machine was initially configured as dual boot (Win7/Win11) then wouldn't the driver problem you refer to also be problematic?
Drivers are specific to the OS and have to be applicable to the machine's hardware.
For example, say you have a Radeon video card. When you boot 7 the OS needs a Win 7 Radeon driver. When you boot 10 the OS needs a Win 10 Radeon driver. That's true whether you single boot or dual boot -- whichever OS you boot needs the right driver for that OS and that hardware.
I didn't think drivers would be a problem... that current drivers would be backward compatible.
That's not always the case, especially since Microsoft and Intel began (around the time Intel's 7th-gen CPUs were released) deliberately putting up roadblocks to thwart the installation of older Windows versions on newer hardware. We've had to rely on people finding various hacks or modified drivers to use W7 on the newer CPUs.
If a machine used a [virtual machine] wouldn't it too face the same [driver] problem to which you refer?
Not necessarily.
The difference is a VM does not get installed on your physical computer, it gets installed on a *virtual* computer. Thus, it needs drivers for the virtual computer's emulated "hardware", not your machine's real hardware. If your virtualization platform (VirtualPC, VirtualBox, VMWare, et al) emulates hardware that is still W7 compatible, you can install 7 in a virtual machine even if the host machine (the real hardware) doesn't support 7.
(If you'd like a backgrounder on virtualization, perhaps
this webpage I wrote will help. It's old, but the general idea hasn't changed.)
FWIW, here's a real-world example of what VMs can be used for: A client's old W7 computer died so he had to get a new computer, of which W10 was his only option. But he uses QuickBooks 2005 and it will not install on 10. QB said he had to buy the new version. But he's nearing retirement and couldn't stomach having to buy a new copy of QB (which isn't cheap) just to go another year or two. So I set him up with a VirtualBox Win 7 VM so that he can continue running his old QB 2005 on his W10 desktop computer. When he retires he'll just toss the VM.