Well gee thanks for the extremely warm welcome guys.
Sorry about that, but there have been a few recent cases of Q&A spam for video capture so it seemed likely.
At least, it's good to know that theoretically it would be possible to record anything I watch on pc, though I'd love to hear a more specific solution on how exactly do you do this.
As long as we are talking about video recording theory it's legal for us to answer this (according to the DMCA it's illegal for a website to even host instructions on how to circumvent copyright):
The theory is that if your computer can play it then it can already decode it. So you record the output. An example of this (though the quality wouldn't be great) is that you could use Cam Studio
, a free screen capture program that can also capture audio from output.
There are probably better ways than that for cases like online video played through flash and silverlight players, and for the most part they are actually grabbing the video file itself (in flash cases this is the .flv file). If you use an extension like Firebug in Firefox you can view what files are downloaded when you visit a page, and get the url of the video from there.
For non-DRM files that is all it usually takes to get the video (you just need a codec to play .flv in your current media player or a stand-alone FLV player) but for DRMed files you will likely need custom solutions that I can't help you with.