xlCompare if easy-to-use tool. You need to do only several clicks to find differences between your files:

If you are using Excel 2007 - select Workbooks button on the Spreadsheet Tools ribbon.

In Excel 2003 - select menu item Compare | Workbooks in the top menu.

This command shows dialog to select workbooks which should be compared:

If your spreadsheet has database structure - decide if you should check compare database values options. These options increase speed of comparison and make difference report more precise. More information about comparing database values you can find in the Comparing spreadsheets which have database structure topic.

Now press Compare button and xlCompare shows you comparison results.