Had a quick google search. I guess what you really need is something to convert powerpoint to AVI, but came up with this:
http://www.greenspun.com/bboard/q-an...?msg_id=005YHL http://www.burnworld.com/software/ph...vd-x-point.htm
which then made me think that the easiest way is to do a screen capture of the slide, which you can do in Windows Media Encoder. Sorry, bit of a garbled response here, but that should set you on your way!