I can set the file format in Windows 7 to NTFS or exFAT. Works with any USB key bought in the last few years.
Windows XP had no problems reading NTFS.
Windows XP had no problems reading NTFS.
If you mean "not made by the Linux kernel or GNU projects", that applies to much (most?) of the software available for Linux.
If you mean "proprietary", then NTFS-3G is GPL: http://www.tuxera.com/community/open-source-ntfs-3g/