Assuming you would like a step-by-step guide on how to change your default browser on Windows XP:
1. Open the Control Panel. You can do this by clicking on the Start menu, and then selecting Control Panel from the list of options.
2. Once you're in the Control Panel, double-click on the icon for Internet Options.
3. A new window will pop up with several tabs at the top. Select the one labeled Programs.
4. In the Programs tab, there will be a section labeled Internet programs. The very first option under this heading is Microsoft Internet Explorer should check to see whether it is the default browser. Put a check mark in that box, and then click OK at the bottom of the window.
5. Close all open windows, and restart your computer for the changes to take effect.