Many users require multiple operating systems especially after the launch of Windows Vista. If multiple operating systems are installed on your system, you would have to select one from the menu each time your PC boots. If you're frequently using an operating system, for example Windows XP, you can configure your system to select Windows XP as the default operating system. To do so:

Double-click the 'My Computer' icon on your desktop.

In the resulting window, click the 'System Properties' button.



Click the 'Advanced system settings' link from the left panel. The 'System Properties' dialog box will appear.

Click the 'Advanced' tab.

Click the 'Settings' button under the 'Startup and Recovery' section.

Select the operating system to be set as default during startup from the 'Default operating system' dropdown list.

Once done, click 'OK'.