Transparent windows

How do I make windows or anything transparent in the game engine?

In 2.45, you just create an image with less than 1.0 alpha, map it to your object, then in the Texture face panel under the editing buttons (F9), select ‘Alpha’ then ‘Copy Drawmode’.
In later SVN builds, the texture face panel has nothing in it, so if anyone knows how to make it work, that would be something I want to know

select your glass object,

Press F to get into UV face mode,
press A a few times untill all the faces are selected,
In the edit buttons, press the alpha button, then copy draw mode…

make a new material,
now in the material pannel, look for the alpha slider, this will control your transparency.
set alpha to around .5, and run the game… the glass material will be transparent…

If you press the Ztrans button in the material window, it will allow a more advanced alpha mode.

the best way is with an alpha masked texture, that way you can paint in the dirt/dust/ice/snow/cobwebs/etc… in the corners of the windows.
It will also allow you to make signs like on store windows, with words, or posters.

if you use Mmph!'s method, be sure that the ‘Use blender materials’ item in the ‘Game’ menu (on the top header) is checked.

@Mmph! - I never knew that you could use the transparency from a material before, but once again, since the Texture face panel in the edit buttons has nothing in it in SVN builds, this method also doesn’t work. Did this get broken in the switch from UV face select mode to just edit mode?