Hi Paolo,
I also have a Thinkpad W541 and scratched my head on how to use the built-in fingerprint reader when running e.g. Windows 10 on a VM-machine from my laptop - and then came across this thread.
After comparing the "Device Manager" both on my VM-machine and on the physical laptop I could see that on the VM machine there was no "Biometrical Devices" listed on the VM-machine. I of course also checked the VM hardware setting dialog if there was a possibility to add such a device, but there wasn't.
So I thought I was stuck. But I have found a solution that is sufficient at least for my needs. I noticed that one of the icons on the lower-right side of my running VM-machine (running Windows 10) - there was an icon that was disabled but when hovered with the mouse it read "Validity Sensors Synaptics FP Sensors (WBF) (PID=0017)".
After right-clicking and selecting "Connect (Disconnect from Host)" there was a new device that showed up in Windows Device Manager "Unknown Device" and when opening that treeviewitem I right-clicked and selected "Install driver" and voila! Now my built-in fingerprint reader can be used when running Windows 10 under my VM workstation!
It is not ideal as it will disable the fingerprint reader on the physical machine's OS as long as the Windows 10 VM machine is running, but I can live with that. And the good part is that Windows(?) is smart enough to automatically re-enable the fingerprint reader on my physical machine as soon as the VM-machine is closed/shut down.
Hope this helps!
