there's a link to "game trailers" and "movie trailers"
I've only been able to get this to work once.
the whole PC to XBMC streaming thing is giving me a terribly hard time
The simplest way to stream media from your computer is through using the SMB protocol. To make this work (assuming you are running Windows XP), all you should have to do is share the folders on your PC that contain the media and navigate to your media from the XBMC under the default SMB bookmark.
For whatever reason, your computer may not be visible to your XBMC (mine at home is not for example), so what you can do is create a shortcut to your media folders within XBMC. There is a syntax that you must follow for this to work, and you may want to setup an XBMC user account on your PC.
For example, if you have a user called "xbox" with password "pwd" on your computer which has IP address 192.168.0.2 and you want to connect to your "My Music" share, the syntax would as follows:
smb://xbox:pwd@192.168.0.2/My Music/
This bookmark can be either added from withing XBMC using the controller (I believe the "white" button acts like a right-click and brings up some menu options), or by editing the XboxMediaCenter.xml file. To edit the .XML file, you must FTP it to your PC, edit it, FTP it back to your Xbox, and restart the Xbox.