**This issue has been resolved in ArcGIS (Desktop, Engine, Server) 9.3.1 Service Pack 2.**After upgrading to ArcGIS Desktop 9.3.1, double-clicking on an MXD document to open it in ArcMap may result in the following error:"ArcGISFileHandler.exe - Entry Point Not Found GetProcessImageFileNameW not found in PSAPI.DLL"
If documents are opened from the file > open dialog box in ArcGIS Desktop, this error does not appear.
At ArcGIS Desktop version 9.3.1, a new 'file handler' application was created to assist with finding the appropriate application to open map documents. This application relies on a file called 'PSAPI.dll'. If the version of this file is outdated on the machine on which ArcGIS Desktop is installed, the file handler application does not properly associate the map document with ArcGIS Desktop.
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