I haven't actually seen Series 3 and 4 on DVD, because they are only formatted for the UK and won't work in US units. (Seasons 1 and 2 are available for the US). This is very frustrating and I'm wondering why the entire series isn't offered to your US customers. If anyone knows why this has happened, or has any suggestions on legally re-formatting the UK version, please let me know. I'm assuming there is a copyright issue that is unresolved.