Hi Shoom,
This is not a perfect solution but it is the only one that I do know: Download free program called Freecorder. It lets you record sounds.Usually on laptops it only records outside sounds so you hear footsteps etc; this one tapes the actual lecture even if your laptop is on "muted" setting. Obviously it is not great since it means you actually have to have the lecture running, therefore needs you to have an hour free..
Can always leave it overnight or whatever - but, put some sort of object onto the keyboard so that it doesn't log off due to inactivity.That's how I do it anyway I'm sure hopefully someone has better option