When clicking on a row in Microsoft Excel, instead of selecting a single row, it for no apparent reason it selects multiple rows.

• First of all make sure you don’t have Extended Selection enabled. Look into left bottom corner, if Extended Selection is enabled, press F8 to disable it.
  
• Click on View tab and in Workbook Views section check which view you are in. If Page Layout view is selected, change it to Normal view.
  
• If able doesn’t help, try slightly changing the workbook zoom level (using a slider in the right bottom corner).
  

Microsoft Outlook 2010
Windows 7
Windows 10