I recently wanted to try a windows only usb device. I deceided to bring up a qemu image and found a few things out that I wonted to put in one place:

for win2k make sure to use -win2k-hack when building the system as indicated in the qemu man page

If your host is an ubuntu 7.10 box, to use usb in the guest, you need to uncomment some lines in a file. This will enalble /proc/bus/usb/devices which is needed by qemu