Before your XP login password is forgotten, you can easily create a password reset disk XP.
Windows XP allows its users to create a password reset disk. Usually, after you installed XP and created a user account on your PC, you would be asked to create such a disc. As for detailed steps to create it, you can follow as below:

1. Open User Accounts in Control Panel.
2. Click your user name.
3. Under Related Tasks located on the left side of the window, click Prevent a forgotten password.
4. In the Forgotten Password Wizard, follow the instructions as they appear on the screen.

(Note: Things you’ll need: a blank and writable CD/DVD or USB Flash Drive.)

How to use this created admin password reset boot disk for Windows XP password reset?

1. At the Windows XP login prompt when the password is entered incorrectly, click the reset button in the login failed window.
2. Insert this disk into the computer and click “Next” then.

If the disc was correctly created, then Windows XP will open a window prompting for a new password you wish to change.

After your XP password is forgotten, your best choice to create a password reset disk is using Windows Password Key.
The service to create a XP password reset disk what Microsoft offers can only help you take precautions against XP password forgotten problem. However, when you truly forgot your computer password, you have to seek for other ways. Here I recommend Windows Password Key - a powerful and professional Windows password reset tool. You can use this to DIY a XP password disk first, and then use the disk to reset the forgotten XP password.

Here’s the guide on how to create XP password reset disk with Windows Password Key.
Step1: Download, install and run Windows Password Key on an accessible computer.
Step2: Insert a blank and writable CD, DVD or USB flash drive to the computer.
Step3: Click “Burn” button to start burning the ISO image file of Windows Password Key to the chosen CD, DVD or USB flash drive.
Step4: In less than 2 minutes, you will get a message “Burning successfully completed”. This means you have successfully created a Windows XP admin password reset disk. Then you just click “OK” to end the process and take out the removable device from PC.

With the burned XP password reset boot disk, you then can use it to start resetting your forgotten XP password.

Source: http://www.blog.lostwindowspassword.com/xp-password-reset-disk/