Microsoft has a free edition of Microsoft Expression, which has the basic functionality of creating screencasts. This way you can create screencasts, and encode them to WMV (or to Silverlight). The free edition is limited to 10 minutes per clip, but this should be adequate for simple short clips.

Microsoft Expression Encoder can be downloaded from the Expression website: http://www.microsoft.com/expression/try-it/; scroll to the bottom to find it.