Windows 7 - Streaming TV from WMC to my Xbox

Lazy day today, I can't be bothered to get my Xbox out of my cupboard to try this

I've got a TV Tuner in my PC, is it possible to stream it via Windows Media Center straight to my Xbox? If so, is it possible to record things straight to my Xbox?

Yes, I just set mine up last night. I would highly recommend a wired configuration. I don't have the new xbox with the built-in wireless, so I can't offer an opinion on its performance. I tried recording some shows and streaming them to my PS3, which only has a G card in it, but the HD streams were just too much for it and stuttered constantly. If you want to run more than one xbox simultaneously as an extender; then a wired infrastructure is pretty much mandatory.
To answer your other question, the Xbox will only function as a Media Center Extender. Therefore, any shows you set up to record will be recorded on the tuner equipped PC. The Xbox merely provides a method of interacting with the host PC.
I know there are several methods to remove commercials from the recordings, but I have not confirmed whether the xbox will understand these modified files. When I set that up tonight, I'll report back.

Here's my setup so far:

Windows 7 Ultimate x64 ->(wired)-> Asus RT-N16 150Mb/s Router ->(Wired)->xbox360 & PS3.

Asus RT-N16 wireless to two laptops. (which seem to handle HD streaming of recorded shows just fine).

My Ceton 4xHD cable card tuner adapter records 4 HD streams simultaneously on 2TB of attached storage. Streaming HD to my Xbox only uses about 12% of the 100Mb/s wired bandwidth. Based off of this, I don't see any reason why up to 4 xboxes can't be used as extenders at the same time with the possibility of two more over wireless-n (but would require more tuners on the host pc).