How to Downgrade to Windows XP

I recommend doing a full wipe and reload, as anytime an OS downgrade or uninstall is performed it seems to cause trouble.

Make sure you have a Windows XP CD, and a valid product key, as you will need to activate Windows XP once it is installed.

Set your BIOS to boot from USB drive or disc drive.
http://goo.gl/iS8Qzz

Backup and Restore Windows Hardware Drivers
http://goo.gl/IvdKtj

Backup and Restore Windows Activation Status in case you change your mind
http://goo.gl/XZRF0H

Fix Windows XP setup did not find any hard disk drives installed in your computer
http://goo.gl/fsY2ff

source

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