I have made a short video-clip about this subject. Get it here:
http://www.sendspace.com/file/dg43sg
Actually it's specifically tailored for Nastja's inquiry on how to remove commercials from her (friends) recordings, but it can also serve as a general guide (I hope :?).
It begins with a screenshot from 'GSpot'. Lots of people, men and women, don't even know/believe such a thing exists and here you've got a screenshot of it :D!! And I've made it especially for you !
Well, in fact, it's nothing hardcore :(. 'GSpot' is a very nice, little proggy telling you almost everything about your recording.
Just take a look at the clip - it's pretty much self-explanatory. Make selections of parts you want to remove (select on key-frames!) and delete those. If you make a mistake, you can undo the last step. Use filters to adjust your image (be gentle with that), de-interlace to get rid of that 'tooth-comb'-effect, crop the dark edges and resize back to the right proportions. Make a short test-sample to review your corrections and if needed adjust those. You will need to re-encode your recording, though. Use your favorite codec: mpeg2, wmv, divx, xvid or other.
In case you get stuck at some point, just ask. If I don't know the answer, maybe someone else does.
Good luck!
k.