I know TheFineArticle is in Linux land but for Windows people with this issue you might look at Sysinternals Disk2vhd.[0]
It can be run from the online OS itself and it can store the resulting vhd on the same disk it is imaging (with space and disk performance constraints).
I find it handy for turning my freshly superceded gaming machine into a VM on my new machine for easy access to files, before doing whatever with my old hardware.
Another marvel is Tom Ehlert's Drive Snapshot[0], which supports "disk image backups of live or offline Windows 2000-2022 systems all in a portable (and bootable!) ~1MB EXE".[1]
I keep my gaming machines for a long time and usually only upgrade the gpu in that time so the main "fast SSD" is much smaller than the "storage disk" of my new machine. But yes, I get rid of the Steam directory entirely and any large media files.
If I wanted to be more careful I could probably just do a full registry export and keep C:\Users\[username]\AppData. But rather than dig around trying to recall and export MORE stuff (when I want to be playing on the new machine...) I'll just keep a copy of the whole thing for reference.
And it'll get deleted down the track when I'm happily bedded into the new machine.
Other tips: if you moved your license for Windows to the new machine, run the VM without networking...
If you are wondering how to get stuff off it with no networking - because you are using (inbuilt to Windows Pro) hyperv instead of vmware - you can mount the VHD disks directly on your new machine while the VM is off.
It can be run from the online OS itself and it can store the resulting vhd on the same disk it is imaging (with space and disk performance constraints).
I find it handy for turning my freshly superceded gaming machine into a VM on my new machine for easy access to files, before doing whatever with my old hardware.
[0] https://learn.microsoft.com/en-us/sysinternals/downloads/dis...