Actually that's the primary thing it's meant to record. I feel I'm not being clear.
Okay, so you have:
- Powerbook
- HDTV
- XBox, connected to the HDTV by component out.
This is what you want:
- To make a digital video recording file (movie) of your XBox on your Mac.
This is what you need:
- A device that can get a video signal into the Mac.
- I'm not 100% familiar with the XBox, but if the XBox can broadcast on multiple outputs at the same time, then you can use one output on the XBox for the TV and another for the Mac. If not, then you must get a splitter or "Y" shaped adaptor to let one signal such as the component signal go to two places.
You never connect the Mac to the TV. You connect the Mac to the XBox.
For instance, you might get this
EyeTV and then plug it into the SVideo port of your XBox. And then it would make movie files of the output. This is assuming the XBox can drive two signals at the same time (need an XBox expert for that). Although, alternatively, if you wanted to do so, you could play your XBox on your Mac screen with this device and record it off of there too.
Does that make sense? The other part that I feel I haven't clearly communicated is that this will be expensive -- the hardware you need is going to cost you as much as your XBox did. Although from your setup it sounds like you can afford it.
One other off-the-wall solution would be to buy a DVR. Then you can use it to record your XBox plus get all the other happy benefits of DVR owning, and also transfer the files off the DVR to the Mac using your local network.

I could do that with my ReplayTV, if I had an XBox.
