I use the a registered version of Easy Model Railroad Inventory and love it, but I don't think you can obtain it anymore. Another great looking one I recently downloaded is called "Yard Office". I was very impressed with its ease of use and its capabilities. Very user friendly I thought. The author and contact info is below. You can download it from various sites as well.
Yard Office Model Railroad Inventory Software
copyright (c) 2005-2009
Software by Jack R. Carter
1327 W. Abriendo Ave.
Pueblo, CO 81004
email: yardoffice@musicmixradio.com