This button is loading the Windows Task Manager which is the part of the MS Windows. beside other tasks it has the ability to manage the Active process and end the existing Processes. below is the sample of Windows Task Manager from Windows 8 but they are quite similar in the other Windows:
In order to end the process first you have to click the Word or Excel process and then click "End task" button. It will load the message as below:
By clicking "End Process" button on the message you end the process associated to the highlighted process.
Return - Office Processes Handler
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