Xbox 360 media sharing with PC

I have followed all the instructions on my Xbox 360 and I cannot get it to recognize my pc. I enabled sharing in the options menu of Windows Media Player 11. WMP 11 sees the 360 and it is checked. The 360 does not see my pc. I am using a Linksys BEFSX41 router which has built in Firewall. I am running XP with service pack 2. I have done all updates. I also had Zonealarm on, I disabled it, that didn’t do anything. Any thoughts would be appreciated