Once you are logged in, go to 'start\control panel\user accounts' and change the offending password. Note that if you did enter a blank password for the Administrator account, now is a really good time to change it. While you are at it, change the name of the Administrator account itself to something else, as this is the account that everyone who may try to gain unauthorized access to your system is going to try to crack first.

To do this: Right click on 'my computer,' and select 'manage.'

Expand 'local users and groups' then open the 'users' folder and highlight the 'administrator' account. Right click and select 'rename' to change it.

Windows XP Home:

Windows XP Home does not let you log in with the Administrator account normally. To access it, you must restart the computer in safe mode, a special 'minimal' mode used to correct errors caused by third-party software, among other things.

To enter safe mode: Restart your system. Immediately after the POST screen, press F8 a few times to bring up the XP advanced options menu. Select the 'start Windows XP in safe mode' option.

Once safe mode has loaded, login with the username 'administrator.' The password is blank by default. You can now change user passwords by going to 'start\control panel\user accounts.' Reboot normally when you are done.

Create a Password reset disk:

Windows XP is a fair bit more friendly than previous Microsoft operating systems based off of the Windows NT kernel, at least when it comes to recovering forgotten passwords. Not only can you set a password hint to help you remember a forgotten user password, you can also create a floppy disk which will enable you to completely reset your password in the event that you cannot recall it.

While this will not help you if you are currently locked out of your system, it can certainly put your mind at ease about the possibility of it ever happening again.

Windows XP allows users to create a password reset disk specific to their user account. This disk can be used at the welcome screen to reset your password in the event that you do forget it.

To create the disk: Go to start\control panel\user accounts. Select the account you are currently logged in as. Under the 'related tasks' heading in the top left corner, click 'prevent a forgotten password' to open the forgotten password wizard. Insert a blank floppy disk and follow the instructions to create your password reset disk.

To use the password reset disk in case of emergency: Once you have created a password reset disk for a specific user, the next time the password for that user is entered incorrectly at the welcome screen, a message will pop up asking if you have forgotten your password. At this point you can elect to use your password reset disk. Follow the instructions to reset your login password.

Note: There are is a possible problem with the above procedure if you have used Windows XP's built in encryption feature to encrypt some of your files and folders, but have not yet updated to service pack 1. Do not reset your password in this situation, as you will lose access to the encrypted data. Once you have got service pack 1, it is safe to use the disk.

Keep your reset disk in a safe location, because anyone else can also use it to reset your password.