nzskater: To anyone looking to view HD (H.264) content without buying a GFX card that can decode it try CoreAVC. I had issues decoding 1080p x.264 content on my old P4 box that I use as a HTPC until I started using this. Is well worth it.
http://www.coreavc.com/
At this stage however PowerDVD is the only codec supported by GB-PVR. I also couldn't get my .ts files recorded from GB-PVR on the test channels to play back on another PC which had CoreAVC installed. As mentioned elsewhere VLC won't play back these files either.