Sharing from Vista to XP

I am at a loss here. I have a Vista Ultimate machine with a huge audio
library. I am trying to share it across a local network to XP Professional
machines. All the machines use OneCare live as the firewall. Network
discovery, File and Printer Sharing, Media Center Extender and Streaming
Media are set to On. When I click on the Media Sharing in WMP11 (Vista
Machine) all it shows for “Share my media to:� is “Other users of this PC�.
I have installed KB922120 on the XP machines to no avail. All machines are
on the same workgroup. On the Vista machine under “Network and Sharing
Center Network Discovery, File Sharing, Printer Sharing, and Media Sharing
are all on. Side note: All the XP machines can access the Vista shared
printer with no problem.