drives in a file chooser

[Volucris]

Is there a way to get a list of the drives available (on win32: c:, a:, b:,
d:, etc.)? Ultimately, I want to make a file chooser in a Tkinter app.
Desperatly I tried

    os.listdir(os.path.abspath('c:\\..'))

but that does nothing useful. Otherwise, I could just confine my users to a
single drive and say it's a security feature.

greg