Try some of these (hope the link works):
http://wuarchive.wustl.edu/~aminet/aminet.cgi?string=pc+amiga+transferI used one program (forgot the name) that was compatible with LapLink, ParNet and NullModem connections.
It would "mount" the PC's drives on the amiga and transfer through the cable. I'll see if I can dig it out if none of the above solutions help.
Please note: It's okay for smaller files, but it's a SLOOOOOOW process.
You could also use null modem cables and terminal programs on both sides.