Just to beat on this dead horse a bit longer, here's the filesystem on my Sony 350:
Code:
ghidorah ~ # file -sL /dev/sdd
/dev/sdd: x86 boot sector, mkdosfs boot message display, code offset 0x58, OEM-ID " mkdosfs", sectors/cluster 8, reserved sectors 36, Media descriptor 0xf8, heads 255, sectors 3141376 (volumes > 32 MB) , FAT (32 bit), sectors/FAT 3062, serial number 0x3e, label: "READER "
And, of course, it is vfat. If the filesystem was something more esoteric, then Win boxes wouldn't be able to read it.