Hi,
just open a backup specification that contains such Windows server, in the Source tab expand the the server, then expand the CONFIGURATION: subtree - you will see what goes there. It is a collection of a number of different configuration databases and stuff that makes up the identity of a Windows OS installation. It's here because, in Windows, most of this information is held in locked files and traditionally couldn't be saved reliably by just pulling all files from the file system.
That being said, it's a really good question if backing up CONFIGURATION: makes any sense today with C: being backed up with the full might of a VSS snapshot, including all the metadata writers we see to jump in since 2008(R2). More specifically, I would ask if pulling Profiles this way is still of any use, given you will then back them up twice anyway. I tend to uncheck Profiles in CONFIGURATION: for a while now, but would really like to know if leaving out the entire tree would create any problems on a EADR of a hosed machine. Anything of relevance should be in the VSS snapshot in at least a crash consistent state - ususally better due to VSS writer integration file system quiesce support.
Never heard any clear words about it, though.
HTH anyway,
Andre.