You might find this article helpful: "How To Allow Users Who Are Not Administrators to Install MSI Packages" http://support.microsoft.com/default.aspx?scid=kb;EN-US;q259459.

>We have an custom app written in VFP7 that runs on all machines in our building. We have converted the app to VFP9. We would like to automatically uninstall the current app and then install the new app when the user logs on. We can do this when logged into the machine as administrator very easily. However, when we attempt to call the setup when logged in as a user we run into access denied or cannot write file errors.
>
>The commands we use are:
>\\serverfilelocation\setup /X /S /v/qn (uninstall old app)
>\\serverfilelocation\setup /S /v/qn (install new app)
>
>The setup.exe files were created with InstallShield.
>
>Are there parameters or settings in InstallShield that will allow the install on a machine logged in as a user without administrative permissions?
>
>Thanks.