How to change booting priority between Window and Ubuntu(Wubi)

Go to Control Panel Home (Start -> Control Panel) -> System and Maintenance -> System.

On the left side pane, under the Tasks, Click Advanced System Settings.

Click Settings under Startup and Recovery.

Reference

http://www.lytebyte.com/2009/02/05/how-to-change-the-default-os-boot-order-between-windows-7-and-vista/