Vista - Does Media Sharing work with Vista Business at all?

On my home network, I have been running Windows XP SP2 until recently, and
using Windows Media Extender to access videos etc from the XBOX360. Then, I
upgraded to Vista Business, and I could no longer access videos on my main PC
from the XBOX. If I run the test from the XBOX, it says that the last step
fails -- it "sees" the PC but won't connect. Thinking it was the usual
firewall port problems, I checked all those out. Also, the XBOX help says I
need to have my PC made part of the Windows Authorization Access Group in my
Active Directory. However, my home server is Windows 2000 Server, and there
is no such group.

Now I am thinking that Vista Business simply does not support Media Sharing,
because it does not include Media Center. Is this so? If that's the case,
I've lost capabilities when I upgraded to Vista, because under Windows XP
there was a separate Windows Media Extender program that I could run to
enable media sharing, even though I did not have Media Center.

Any help? Thanks.