How to Reinstall an Old Version of Windows XP

1. Back up all files to an external hard drive, flash drive, or CD/DVD.
2. Insert your Windows XP installation disk and restart your computer. Press any key to boot from the disk. Press 'F12' during the boot process and choose 'CD-ROM' if you aren't prompted to boot from disk automatically.
Be sure the version of XP you're installing is actually an older version. Choosing Windows XP SP2 or earlier will guarantee your copy is an older version.
3. Press 'F8' to agree to the license agreement.
4. Choose which partition you wish to install Windows XP on. If you only have one partition, press 'Enter'. You can also delete and create new partitions if needed.
5. Choose to format using a quick 'NTFS' format. This process can take up to 30 minutes depending on the size of your hard drive.
6. During the GUI setup wizard, you will be prompted to change the time, computer name, and network settings. You will also need to input your license key.
7. Restore your files to the computer once the system has rebooted.
8. Activate your product. An activation notice will appear in the notification tray when you reboot your computer. Click the notification, connect the internet, and choose 'Activate Over the Internet'.