FWIW -- I had a similar problem with VMs going randomly down -- it wasn't windows but various BSD and Linux VM's. Sometimes they would run a few days, other times they would lock up every other day. Logs didn't help because when the VM locked, logs were not written. I even had the xcp-ng installation lock a few times, although it was usually on of the VMs. I started searching for faulty hardware and eventually SMART tested all the drives and mem86 the RAM. Turns out I had some bad RAM modules which I later RMA'd. With new RAM (after after thoroughly testing it), I haven't had any lock ups. I'm not sure this will help you at all.