Everyone agrees: old houses are beautiful. The guys from This Old House would know—they've renovated tons of them. But with the high cost of renovation and upkeep, from replacing leaky windows to installing more energy efficient heating systems and appliances, is it better to buy a charming old house and improve it or to build a new one from scratch? Norm Abram and Kevin O'Connor of "Ask This Old House" took your questions and heard your success stories (and horror stories, in some cases) about renovating vs. rebuilding.