Laplink are still (surprise surprise!) in business -
www.laplink.com - and offer PC-to-PC transfer software and a special cable for USB to USB transfer ...
The old Laplink software won't work with XP because it was (is) restricted to the old DOS naming convention (8 character filename + 3 character extension) (there's a name for that which I can't remember ...)
There's also a German company that offers a USB to USB cable:
www.vivanco.com