MCEBuddy takes your LARGE Windows Media Center television recording files and makes them small saving you disk space.  It also removes commercials and converts your recordings into formats that are usable on other systems and handheld devices.  It does all of this automatically with a minimum of fuss and little or no technical knowledge required.

MCEBuddy is an automated service for Windows Media Center XP, Vista and now Vista 64 that converts the Media Center native video format (DVR-MS) to a user-configurable file format (WMV, DivX or H.264).

Source: http://mcebuddy.com/