Window Casings

Hi All, I have HD, 2012, and mostly love it. A problem I get frustrated over is with window casings. The has different casings for my windows and doors...but I can't ! I click on a particular casing, then click on the existing window and..nothing. :o( Is there a secret to this ? I'll appreciate any help. Thanks.
Barb

Comparing my Architectural 2010 with the Pro 2012 trial version, it looks like Pro can change the Molding Profile for Casing applied to Doors and Windows in their respective Specification dialogs, but Architectural can't. So, I think that's a Pro-only feature.