I've just stumbled upon a nasty little problem with Windows XP, laptops, and the NumLock key.
Windows attempts to remember whether or not the numlock key should be on, but there's several different "states" that the machine has to remember for. It remembers for each user, and for the "no user" logon mode, meaning that if it defaults the the one you don't want, it can be extremely hard to change.
Okay, this sounds like a simple annoyance, just hit the key when you need to use the keypad, right?
The problem comes in when you're on a laptop and numlock is on during the logon screen by default. For most of us, the numlock key is that stupid button that makes the keypad over at the right of our keyboard do weird stuff if it's off. For laptop users, the numlock key turns a portion of their lettered keyboard in to a numerical keypad.
When this happens on the logon screen, you can't see that you're typing numbers instead of letters, because your password is asterisked out.
You can log in by figuring out what's going on and hitting the numlock key, but the next time you log out, you're back with the same problem.
Here's the voodoo you have to do to fix it.
* Log in
* Turn numlock off
* Hit ctrl-alt-del to log off (don't hit start->shutdown->logoff)
* You'll now be back at the logon screen, and you'll notice that your numlock key is maddeningly back on
* Turn it off once more, but don't log in
* Hit "shutdown" on the logon screen and reboot your computer
* Upon rebooting, it should remain off. You've now set the default setting for the numlock key during logon.
* (this would, of course, work in the reverse if you wanted to change the default to on for a normal keyboard)