Kari is the Hyper-V guru. This article of his on moving an XP Mode VM from Win7 to Win10's Hyper-V may give some hints...am trying to get an old (Vista VM) working but its giving fits
It was created by using hyper V but the old win 7 version.
Potential issues: (1) Newer Intel processors (Haswell and above) do not support Vista, (2) NVidia drivers no longer support Vista, and (3) Vista predated USB 3.0. Vista is best run on old hardware. Isn’t Windows 7 old enough for use in 2021? It’s possible to make Win7 look just like Vista, and you could even install obsolete browsers on Win7 if you want the Vista experience.The win 10 HyperV keeps crashing.