And still sitting in some quiet corner of the intarwebs you might find a Star Gate file transfer kit. Just follow the instructions to braid your own Mac-PC null modem cable. Once installed (pretty simple setup) you might forget how to swap floppies.

P.S.: this will work only for you, if you have a free serial port on each side (RS422/LocalTalk port and RS232/communication port).

P.P.S.: I did not try this on any Win7 equipped machine. Would a software designed for WinXP be executed under Win7, including permission to access some port directly?