i had major problems with sharing the content on my pc. i have gigs of vids and pics and music but was only showing 32 video when i have hundereds. the reason for this is the 360 only supports one or two type of media main three wmv wma and mp3 so anything other than these and possible a couple more will not be found. i have looked all over and have seemed to have found a solution as mentioned earlier here
Just got the XBOX360 yesterday and was loooking to see what options I had with Win2K server and streaming .. Stumbled across
http://www.tversity.com/Works fine as a picture, music server to the Xbox

install was a dream .. simple
Have not tried Movies yet, however thats what it was first created for so should be OK ..
Also offers web media options ie can stream pics, music from the web..
Hope it helps some others who may not be able to run the MS offerings
TVersity lets you play almost any thing and gain access to almost anything. rule of thumb is if you can play it on WinMP11 you can play it on your 360.