Problem with os.listdir and delay with unreachable network drives on Windows

[Read Roberts]

I wrote my own directory browser in order to get around a bug where 
tkFileDialog.askdirectory()  can't handle non-ascii paths. However, I 
have a problem where I call os.listdir() on a  mapped network drive, 
e.g. os.listdir("Z:\\"), and if the network drive is unavailable, the 
UI hangs  until the OS returns with an exception because the network 
shared drive is unavailable.

  I would like to work around this by simply not looking into  mapped 
drives that are not currently mounted.  Is there some way to check 
the status of mapped drive to see if it is currently mounted, or a 
better solution? ( I use the call win32api.GetLogicalDriveStrings() 
to get the list of available drives).

Also, is there any way to enumerate remote volumes that are mounted 
by not mapped? I can't easily find this in the win32 stuff or via 
googling. The win32net calls to enumerate servers and shares sound 
likely, but don't show such volumes on my system, although I may not 
be using the right arguments.

I have the current Windows binary install of Python 2.3.4 on my 
Windows XP system.