Disable All Accounts - Administrator / Guest Account

I was just trying to get rid of the welcome screen that appears everyone windows xp start, so I disabled ALL the accounts (including administrator & guest account) in Administrative “My Computer> Local Users and Groups” I showed 3 accounts: One in my name, another "Administrator" and third one "Guest". I disabled all of them When I rebooted the pc, the windows xp welcome screen appeared but it did not show any accounts (i.e. I did not have any account to click to). I also tried pressing CLT + ALT + DEL twice to get the window where Username and Account password are to be typed but it doesn't work. It says that "Your account has been disabled. Please Contact System Administrator" (Even the administrator account give that message). I tried typing everything...