I know the Schwarzwald very well. Greets from Baden-Württemberg !
Anyway, I did as suggested. Using LiveCD / gparted, I sized and formated 160meg with ntfs. I made a couple of folders. Reboot into Windows 7 and there is no view available of my newly created storage.
Reboot from hard drive into Ubuntu. Created a new folder 'share_u', closed the files window and right-click the partition icon (looks like a disc drive in the side panel of Home file viewer) and selected Share. That caused Ubuntu to install Windows-sharing and wanted to reboot, but before that happened I canceled that dialog, and selected options for Guest and Users can use. I noticed Linux Windows-sharing also added a desktop icon for my newly-created 160gig so i could unmount if desired.
Booted into Windows 7, and whoa! there is a new icon in Computer Navigator. Windows assigned Letter drive E:/. Double-click that and I see my folder 'share_u'.
And, I type all this for those that follow. I was about to reformat my exFAT to FAT32 to see if that made any difference exposing partitions to a dual-boot. I'm glad your suggestion proved to be a better and simple solution: larger capacity, larger files and I don't have to rig up an external USB drive. Users see familiar icons in both OS to save their files.