This is a workaround solution for anyone encountering the prompt for credentials when opening Excel documents:1. Navigate to C:\Program Files\Microsoft Office\Office12[or Office14]\EXCEL.EXE
2. Right-click on the Excel executable and select 'Properties'
3. Switch to the Compatibility tab.
4. Change Compatibility mode to 'Windows Server 2003 (Service Pack 1)' and click 'OK'.
