The USB wifi device is a Ralink rt2750 device. It is supported by the rt2x00 driver family, and in etch you can just follow these steps:
cd $(mktemp -d) m-a -u . prepare m-a -u . get rt2570 m-a -u . build rt2570 sudo dpkg -i rt2570-modules-$(uname -r)*deb
In order to have a predictable network name to write rules for, I added the
SUBSYSTEM=="net", \ DRIVERS=="rt2570", \ KERNEL=="eth[0-9]*", \ NAME="rt"
If anyone knows where this device is, physically inside the computer, I'd love to know I'd probably put it in something else.