I tried getting my XBox 360 to work with my Media Center PC yesterday afternoon, but I've given up for the moment. I have a Toshiba Qosmio laptop (an F15-AV201 to be exact) running Media Center 2005. I did the necessary download and installation on the PC, and was able to get the 360 and PC to 'see' each other over our wireless network after taking the 8-digit code the 360 gave me and entering it at the appropriate time during the installation on the PC.
The 360 was able to display the familiar media center menu, but gave a frustratingly generic 'Video Error' when trying to view live TV. I also discovered that the problem extended further than just with the 360 integration....my laptop itself now cannot show video! Media Center gives an error message and then crashes. It then tries to create and send an error report, but the processes never successfully finished sending the error report. So, not only do I have no integration, but my laptop's TV playing capabilities are broken.
I had created a system restore point before beginning the whole process, so I can easily rollback if I want to, but since I almost never use the Media Center capabilities as it is, I won't bother for now.
I didn't have much luck researching the issues yet, but will keep trying.
Overall, I'm still having a great time playing Kameo, Bejewelled, and Hexic. Once I'm done with Kameo I'll be concentrating on Condemned and finish that off, and then probably will end up getting Perfect Dark Zero to run through the single-player campaign, and then play co-op with my friend Scott over XBox Live. He'll be trying out Kameo too when I'm done with it, and if he likes it and gets a copy we'll be playing that co-op too. (I have a feeling once he sees the graphics and gameplay of it, he'll be getting a copy, even though this particular genre isn't his first choice....)