Thanks a lot for your quick reply!

Actually, your comment somehow got me on the right track:
I remembered that this xeox pro has a switch on its bottom to toggle between XInput and good old DirectInput mode... It was in DI-mode - and once I switched it to XInput, voila, it appears as xbox360-kind with all its sub-sensors :)

So, issue for that one solved. For the (pretty antique) other one I'll provide you with a screenshot asap.

EDIT: here it is, the screenshot for the Speedlink SL-6535 Strike². I suppose the issue is simply that sensors.lib only likes modern XInput-devices?