The difference between display name and user name...
Your display name is what you see when you click on your name, assuming that you are using the "Welcome Screen" Feature by WinXP. Your display name is not necessary your username or "computer account name"
This guide will show you how to find your user name
Click on Start\Run
Type "cmd" without quotes
It should bring up a black window, with white text. This window is the command-line user interface for advanced operations
In the command prompt, type "set" without quotes
Your user name is under "USERNAME=myUserName", typically the third line up from the bottom.