After installation of Windows 7, dual-boot with Windows XP is Windows 7 which is positioned in the boot option by default (being the last set).
On the start screen, so it is Windows 7 which is highlighted and will start automatically after the counting of the period specified.
To start on XP, it will select it with the directional arrow "top" of the keyboard.
To change the startup option by default, so be it Windows XP that starts automatically:
* In Control Panel, then System and Security, click on System
* Click on Advanced system settings (in the left pane)
* Click on Settings section Startup and Recovery
* In the System startup, click the drop down arrow and select Windows XP. OK by OK
At the next boot is Windows XP that will be highlighted and will start automatically without further action by the user.