To get your chart to fill the entire page in Excel 2007, you can follow these steps:

1. Click on the chart to select it.
2. Go to the "Page Layout" tab in the ribbon.
3. Click on the "Print Area" dropdown and select "Set Print Area".
4. Go to the "Size" dropdown and select "More Paper Sizes".
5. In the "Page Setup" dialog box, select the "Page" tab.
6. Under "Scaling", select "Fit to:" and set both the "Width" and "Height" to "1 page".
7. Click "OK" to close the dialog box.
8. Go back to the "Page Layout" tab and click on the "Print Titles" dropdown.
9. In the "Page Setup" dialog box, select the "Sheet" tab.
10. Under "Print Titles", click on the "Rows to repeat at top" field and select the row(s) that contain your chart title and axis labels.
11. Click "OK" to close the dialog box.

Your chart should now fill the entire page when you print it. If there are still gaps between the chart and the top/bottom margins, you may need to adjust the margins or the size of the chart.