See 'HOWTO: Installing an Application For All Users on Windows NT/2000 From the Command Line Argument or Custom Actions' http://support.installshield.com/kb/view.asp?pcode=ALL&articleid=Q105063

>How can one build setups that install and register files for all (vs. the current) users on a specific PC (NT/2000/XP? Ideally, what we would like to be able to do is detect whether the currently logged in user is an administrator or a standard user. If they are an administrator they get prompted with an option to install the software for just the administrator or to install the software for all users. If they are a user, the software gets installed only for the current user.
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>BTW, this is the technique that Quicken setups use.
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>Thanks!
>Malcolm