There is however a second possibility. Third party software that can load themes into Windows Vista. These programs usually patch the files themselves. One of those software programs that can install Vista themes automatically is Style Selector.

Style Selector is a free 200 Kilobyte portable application that runs on 32-bit editions of Windows Vista. New Vista themes have to be moved into the Styles folder. The Vista theme has to make use of a .styles file to be recognized by the software program.

Vista themes that have been moved into the folder are automatically recognized by the application. Selecting the Vista theme in the list of available themes and clicking on the Apply button will load that theme into Windows Vista.

The Startup box can be checked to apply the Vista theme during startup so that the new theme will be available even after a reboot of the system. The same preferences allow to pick a default font and font size which will then be used as the standard font in Windows Vista.

Update: Style Selector is no longer available. The developer website returns an error and no download portal seems to carry the download.