Yes, it is possible to change the default table style in Excel 2007. Here are the steps to do so:

1. Open a new workbook in Excel 2007.
2. Click on the "Home" tab in the ribbon.
3. In the "Styles" group, click on the "Cell Styles" button.
4. Right-click on the table style that you want to set as the default.
5. Click on "Set as Default Table Style" in the context menu.
6. A dialog box will appear asking if you want to set the default table style for this workbook or for all new workbooks. Choose "All New Workbooks" and click "OK".

From now on, every new workbook you create in Excel 2007 will have the table style you selected as the default. You won't have to change the style every time you create a new table.