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When you have the Outlook 2003 program window open for a long time, Microsoft Outlook may stop responding. Also, if you view the Processes tab in the Windows Task Manager dialog box while Outlook 2003 is running, you may see that Outlook is using an unexpectedly large amount of memory.
While Outlook 2003 is running, it periodically pages memory in and out of the process address space. When the memory that is free is large, Outlook 2003 is permitted to have more pages in memory. This increases the memory that is being used by Outlook 2003.
If another program requires memory, Outlook 2003 will release memory. When you minimize the Outlook 2003 program window, the pages are switched so that the pages that are not required for user interaction are switched out of memory. When you maximize the Outlook 2003 program window again, the pages that are used for user interaction are switched in to memory, and the memory usage begins to increase again. This behavior could when you are working with a large personal folders (.pst) file or a large folder (.ost) file as well as other actions within Outlook 2003.