Show me how to use data validation in Microsoft Excel 2007

Excel -> Microsoft Excel 2007

Problem: I need to ensure that only certain types of data, or data within specific ranges, is entered into certain cells in the spreadsheet.

Open Microsoft Excel 2007
Select a cell or a group of cells
Click on the "Data" tab
On the "Data Tools" section, click the "Data Validation" button
Click the appropriate value from the "Allow:" drop-down menu, and any subsequent menus
Click the "OK" button