Rename computer administrator in Documents and settings folder

I have just had my computer wiped and xp put back on
However the person who did this for me has called me John by mistake!
I can change it in my user account

But in C Documents and Settings I may be John forever unless I have to lose my computer for it to be wiped again

Any quick and safe way to do this please?

When I try it says its a Windows file and cannot be re named
Please help

 

I just tested that. I created an account and gave it administrative privileges. Booted in and out of the account. Booted back in to my regular account and renamed the new account in users and documents and settings. Booted back out and logged onto that new changed account without a problem. Worked for me!

 

But microsoft says dont rename system files and wont let you do it
Dont want problems afterwards