I haven't dabbled into this too much but here's what I do know and options I can give you.
- Use FRAPS. It'll only do it for a minute unless you get the paid version
- Some broadcasting software can also save a local copy. I know LiveStream did this, but the quality can be meh depending on the material.
- If you're wanting higher quality recordings, are willing to spend some money, and you have access to another computer, I'd suggest getting a HDMI capture device and use your laptop's HDMI port. Clone the view and have the other computer record the footage. You could probably do this anyway with the laptop by itself, though. The HDMI capture device will handle the heavy lifting too.
As for commentating, you can do it at the same time by setting your microphone in Windows' audio settings to "Listen to this microphone". This will inject the microphone into the output mix. I don't know how well this works in practice though.