Are you trying to install from the logon? If so, then you have to hold the script until the install is complete.
Wintendos do a smoke and mirrors with a temporary Z: drive mapping during the logon and tear it down after. You may be able to do it by mapping to the drive where the install is.
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Give a man a fish and he will be back for more. Slap him with a fish and he will go away forever.
