You need to install Logon Studio first. It's a free logon changing program for XP and you can get it here: [link]
Then download the logon and unzip the file. Inside are 2 logons, a widescreen and standard res. Doubleclick on whatever one you need and it will open up the Logon Studio window and show in the list of available logons. Choose it and hit "apply" and that should be it.
If you have any problems, let me know. And yes, it seriously works.