I tried that; it doesn't work for two reasons. First, the dongle for the software lock won't work in the virtual XP machine. Second, the virtual XP machine lacks the ability to use devices attached to SCSI adapters or Firewire ports. The scanner is a Firewire 400 device, so the virtual machine is useless. Still I can use the virtual XP machine to use less demanding hardware that only need USB access.
So how come the manufacturer of your scanner wouldn't write the drivers for Win7?