This plugin will allow 100% pretty permalinks on IIS 6/7.
Fed up with IIS not providing permalinks? Don't have access to the IIS control panel on your host? Then wp-aspxrewriter is for you!
Allowing URLS such as: http://www.pynchon.net/discourse/2008/03/06/24/two-amusing-pynchon-posts.aspx this is the easiest way to enable completely pretty permalinks on IIS 6 or IIS 7.