Changed my XP username, but it didn't change everywhere

That's a feature of XP, when you change your name, it will change it on the surface, but still keep your real username. So that's why Sysmetrix is showing you your old name. The only way to change it completely is to make a new username. If you do create a new name, you can then remove the old one, XP will give you an option to delete or keep the files of your old name.
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yea... i believe sysmetrix gets the username from the name of the user folder in documents and settings, unfortunately because of windowsxp security settings, that name is unchangeable (even by windowsxp lol), so creating a new account and getting rid of the old one is the only way to completely change it

Thanks folks!

I haven't had a chance to try this yet, but a question occurred to me: Will this affect my ability use my registered software. ? Or is the name associated with them a different thing altogether? Thanks.

I don't think it will affect your software. What might happen is when you create a new username, some software could become invisible to your new name. It will still be there on your HD, but not in your 'All Programs' menu. If that's the case, all you need to do is create the links yourself or reinstall the software.