Your PC treats partitions the same way as it does drives. So, if you have 1 hard drive with 2 partitions, your computer will treat them as 2 separate drives. Either you have partitions on one, or both of your hard drives that you may not be aware of, or one of your applications created a virtual drive for some reason.
I'm guessing that in your case, the extra/virtual partition is used for meta data (Tags), and not for the actual music files themselves.
I'm guessing that in your case, the extra/virtual partition is used for meta data (Tags), and not for the actual music files themselves.

