I don't even think AVCHD UpShift will help because it turns AVCHD into HDV which still requires a minimum 2.8GHz processor. Not even GearShift will help because it will still take forever to create the DV proxies. All of these solutions are for people who don't want to go dual core or quad core yet but this person doesn't even have a single core capable of the job. He really needs a new PC for working with HD video.
~jr
www.johnrofrano.com
www.vasst.com