Perhaps a little more information on your enviroment and long term goals of what you want to achieve would be in order.

If you have mostly a 2000/XP client infrastructure I'd highly recommend NOT showing your users the logon script and let it do everything hidden while the user continues to work.

Most of our desktops process our script in under a minute, but sometimes due to all sorts of odd reasons the script may not complete for 20 minutes or more, but the user doesn't see or know it is even doing anything in the back ground, vs being forced to watch something, if it takes 20 minutes then they can't do anything till the script completes.