Re: Dimension 2400 Keyboard Failure
One thing I don't see in your posts; have you tried going to setup (F2 on starting the computer) and navigating the setup menus? If you can do that perhaps the keyboard driver in Windows is what's giving you the problem. You might be able to restore it if your mouse still works by going to the Device Manager and removing the keyboard from the list to see if Windows will reinstall it on the next start-up.
Edit: Oops, you have a password. I guess that means you can't get to the F8 startup menu, either. You might have some luck with a repair installation with the Windows installation CD.