Lifextender is a dead-simple commercial-removal application designed exclusively for Windows Vista Media Center users. There is ZERO configuration required, however, there are plenty of options if thats your thing.
Lifextender is pretty simple. It scans the directory that Media Center records TV to every X minutes for new TV shows. All new TV shows are queued up to be analyzed and scanned for annoying commercials. After a show has been analyzed, a new file is created from the original with commercials cut out, around 3/4 the original size. The original show is then replaced by the new, commercial-free show. Rinse and repeat.