After you have chosen to install Windows XP, you will get a Welcome to Windows Setup dialog box that will ask if you want to upgrade or install the new operating system. You can make your selection using a drop-down menu and then click Next to start the upgrade or installation.
The next dialog box is an important one, at least to Microsoft. It is the License Agreement. Be sure to read the agreement, using the scroll bars to view the entire text. When you have read it and are ready to continue, select the radio button labeled I Accept This Agreement and then click Next.