I vote for "Stick with XP and stay off the internet" as the easiest option.
But may I demonstrate my geek credentials and explain what is going on?
Running a DOS program in XP is actually running a DOS emulator on top of XP. As long as XP has drivers for the storage device and the format is understandable by DOS as a disc drive device, the your DOS program can "see" the device. The same applies to all the "NT" lineage if Windows operating systems.
However FreeDOS running as the full operating system has to gave appropriate native drivers available so anything new-fangled (in DOS terms) like USB will not be recognised unless some form of DOS driver is available. Because DOS has very limited memory availability then such drivers are very tricky things. To my surprise however there are some people who think it can be done - see
http://www.freedos.org/technotes/newsitem/149.html it could be worth a try.