Method 2: Using the forgotten password diskette
If you have forgotten your Windows XP password, however have created a forgotten password diskette earlier to use the diskette follow the below steps.
1 At the Windows XP login prompt when the password is entered incorrectly click the reset button in the login failed window.
2 Insert the password reset diskette into the computer and click Next.
3 If the correct diskette Windows XP will open a window prompting for the new password you wish to use.

Method 3: change the lost password with another account with administrator right
Reboot the computer into Safe Mode. Additional information about getting into Safe
When logging into Safe Mode you should be prompted with an option to what account you wish to use. Select the Administrator account. If prompted for a password try simply pressing Enter on the keyboard for no password. If this does not work, try other passwords you may have used. If you’re unable to log into the Administrator account skip to the next suggestion.
Once you’ve logged into the Administrator account open Control Panel and User Accounts.
In User Accounts select the account you wish to change the password for, click change password and then enter the new password or click remove the password to remove the password from the account