http://pubs.logicalexpressions.com/pub0009/LPMArticle.asp?ID=305 This method works and is relatively simple. I've done it before. Basically a repair installation (which will not wipe out your files or anything like that, it just reinstalls core windows components to their original state) with a little tweeking added at the end. Hope this helps! It's a bitch to get locked out. Alternatively, if nothing you try works then you can slap the hard drive in another machine as a slave and go in with windows explorer and manually copy all your files and important stuff to the drive in the other (friends?) machine. It's a last ditch effort but it'll save your data. Things like your my documents folder can be found in the directory "C:\Documents and Settings\[insert user name here]" It could be under a drive other than "C" depending on how you have it set up. If you use the slave method it'll prob show up as E: or something in your friends computer. Basically the last letter in sequence if you put it in a friends machine. Then just format the drive and start over with a new windows install. This could be a good option as windows XP tends to need a reinstall every year or two anyway to keep it running tip top, even if you protect it regularly with adware and virus scan software. If you do the format and reinstall I'd recommend a program called Dban (i think) to securely wipe everything from the drive so it cannot be recovered. That way any sensitive files you've deleted in the past like tax info etc will be permanently destroyed. Wow that got long real quick.
Did you log into safe mode, or safe mode with networking? You're going to want to make sure you booted in safe mode WITHOUT networking. that might be your problem. An easier way to fix it though: I would go into safe mode, back up all of your file on an external drive, and then reformat the entire disk. After that, don't bother with account passwords or anything. they are always way more trouble than they are worth.
Can you get to cmd? If so run net user user_name new_password Of course change user name to the name of your user and put in what you want the new pass to be. Secondly, if you did put in a live boot linux cd you could also change your password...so..it IS A WORKAROUND....but yeah
get to a cmd screen by booting in safe mode. Type CONTROL USERPASSWORDS2 you will be able to change the password here