AdMartin was correct.
2.1 was the first AmigaOS that included CrossDOS. It's available as an add-on for all AmigaOS versions, though. Actually AmigaOS 2.04 and 2.05 are the least-supported versions, as you had to hack the 1.3 CrossDOS to work on them.
If you're trying to link an Amiga with a PC, though, you shouldn't need CrossDOS at all.
Honestly, if you're really this determined to write disks that an Amiga can read, and don't have any previous Amiga experience, the easiest way would probably be with a Catweasel card for your PC.
Catweasel - JSchoenfeld