The setup.exe application for the ArcGIS for AutoCAD Build 355 32-bit version does not run on a Windows 7 Enterprise 32-bit operating system.
Users receive a dialog box with the following message: "This installation package is not supported by this processor type. Contact your product vendor."
The issue was likely due to a 64-bit version of ArcGIS for AutoCAD being installed on a 32-bit computer. Please refer to this page: http://appsforms.esri.com/products/download/
to download the correct version of ArcGIS for AutoCAD. Note that the current release of ArcGIS for AutoCAD only supports 64-bit installations.