You'll have to modify the furniture library SH3F file where these windows come from, removing the properties starting by [font=courier new]doorOrWindowSash[/font] from the PluginFurnitureCatalog.properties file found in the SH3F file (see also this thread)
For the windows in the default catalog, change the same properties in the DefaultFurnitureCatalog.properties file found in Furniture.jar file. This file can be found in the installation folder of Sweet Home 3D.
If you want to turn off this drawing from a plug-in, it's not possible.