What's "Generic volume shadow copy"?

I'm doing a complete system scan at the moment (AVIRA is my AV). I'm
doing it after a restart, because my email-and-news software (Turnpike,
quite old) behaved oddly once or twice.

It may have nothing to do with that fact, but twice a "new hardware
found" popup has appeared, and when I let it proceed to the point where
it tells me what the new hardware actually is, it has said "Generic
volume shadow copy". (I cancel it at that point.)

I haven't added any new hardware (it's a netbook, with nothing plugged
into it other than the power supply at the moment). I _have_ added a
"subst" into my startup sequence, but that was a few days ago, and the
popups have only appeared on this session.

Any idea what it is? It _sounds_ as if it just might be malware, but I'm
fairly careful, and have never had any in decades of computing. (Avira
says it's done 41.3% - scanned 47215 objects - so far, and not found
anything.)

I'll just go to Google it ...
--
J. P. Gilliver. UMRA: 1960/1985 MB++G.5AL-IS-P--Ch++(p)[email protected]+Sh0!:`)DNAf

.... back in the olden days ... Britain was entirely made of wood and lit by
one enormous candle, tended by the Queen
- Steven Moffat, Radio Times, 24-30 July 2010