Excel 2000 to 2003 - Use Excel's main menu select View>Toolbars and check that XLC Tools is selected. If XLC tools does not appear in the list of toolbars then it is not installed.

Excel 2007 to 2010 - The XLC toolbar appears on the ribbon under the "Add-Ins" tab. If it is not visible then XLC has not been installed.

Common installation problems: