How to serve videos on computer to an xbox 360 or PS3

smokey- Yep, I'm a bit slow. :) Read right past where you said it does see the Media center on the computer.

Did you set the sharing attributes of the other computer folders you wish to see,plus have a wmv file in that folder? XBOX should see the WMV video files immediately. I had to put XBOX online in the store for an update to see the MP4 files. I have the additional folders set to guest sharing. IMO, vista is more difficult to set up but now I can see several vista and xp computers on my XBOX360. If sharing is set on the computer those folders are listed with the different computer names in the XBOX menu under "videos"; likewise under music, etc.
 
I've been using TVersity for a while to get videos to my xbox and it works great.

TVersity - Home

They've got a pay version that even allows hulu streaming, but I haven't tried it.

Just install it, set up your folders where your videos are and then check your xbox. It should show up in the sources as "TVersitymediaserver@homepc" or something like that.

You may have to tweak the settings on the TVersity software to get the video to show in full resolution, but it's pretty easy to use and it's handled everything I've ever thrown at it.