There's no way you can do this. When you format a partition you create a volume which is probably in NTFS filesystem format, and the files and folders exist within this volume as their main container. If you were to now take some of these files and folders out from that mount point volume (which is given a drive letter), you would end up with a RAW format of data, which wouldn't be recognized by Windows, and getting your data back would be pretty tough unless you were to view it with a utility like Linux which can read that RAW data. You can mount a folder from a volume/drive, but in order to do this, you would still need to have the initial drive with all of the folders, otherwise, this "folder" you're talking about mounting as a drive, would just be the drive itself.
I don't get why you want to do this. You can't mount folders by themselves as drives. You can MAP them as virtual drives, but they still need to be able to point to a reference from the initial volume and it's containing folder.
Unless you really really want to go through the trouble, and risk your data in the process, by creating a new volume, moving the folders and files you want, and deleting the filesystem data from the original volume rendering the filesystem for that volume "corrupt" and therefore, leaving it behind as a RAW data format because it's no longer identified as NTFS (or whatever filesystem it's formatted with, FAT, FAT32, etc..).