Losing your Windows XP Professional CD key (aka product key) might not seem like a big deal but there's a good chance you'll end up needing it. You need the XP Pro CD key that came with your operating system before you can reinstall it.
The easiest way to find a lost Windows XP professional key is to download a free key finder program and have it automatically search your computer for your Windows XP Professional key. Keep in mind, however, that your XP Pro CD key will only be found if you run it on a computer with Windows XP Pro still installed.
The Windows XP Professional CD key is encrypted in the Windows Registry so you'll need to use one of the product key finder programs to locate it. There isn't an easy way to find an XP Pro CD key manually.
If you need specific instructions on finding your Windows XP Pro CD key with a product key finder, see my How to Find the Windows XP Product Key Code guide.
These key finder programs are perfect for finding lost CD keys for operating systems like Windows XP Professional and even other kinds of programs and games.
If you still can't find your Windows XP Professional CD key, you may, unfortunately, need to purchase a copy of Windows XP Pro all over again.