Powerpoint 2007 to screen capture

Is it possible to use Windows media encoder to capture a powerpoint 2007
presentation and save it as a .wmv in windows vista?

I am running Vista bussiness and I use Powerpoint 2007. I would like to
convert some presentations with narration to video format, but my budget is
restricted. I tried Camtasia, which works well. But they only have a 30 day
trail, the full version is expensive, especially with our local currency
dropping to an all time low.