What are the Startup folders for Excel?

Windows

(The following assumes you installed Office into the default location.)

Microsoft Excel 2013 for Windows:
C:\Program Files\Microsoft Office\Office15\Xlstart

Microsoft Excel 2010 for Windows:
C:\Program Files\Microsoft Office\Office14\Xlstart

Microsoft Excel 2007 for Windows:
C:\Program Files\Microsoft Office\Office12\Xlstart

Microsoft Excel 2003 for Windows:
C:\Program Files\Microsoft Office\Office11\Xlstart

Mac

Microsoft Excel 2011 for Mac:
Hard Disk:Applications:Microsoft Office 2011:Office:Start:Excel

Microsoft Excel 2008 for Mac:
Hard Disk:Applications:Microsoft Office 2008:Office:Start:Excel

Microsoft Excel 2004 for Mac
Hard Disk:Applications:Microsoft Office 2004:Office:Start:Excel

Microsoft Excel X for Mac
Hard Disk:Applications:Microsoft Office X:Office:boot:

Excel Microsoft Excel 2001 for Mac
Hard disk: Microsoft Office 2001:Office:Start:Excel

Microsoft Excel 98 for Mac
Hard disk:Microsoft Office 98:Office:Start:Excel