Hi Leiw
You can change you Office User Name by doing the following:
1) Click on the top right Office Icon [normally beside the "Save button"]
2) Click on the "Word Options" button [on the bottom right hand side of the menu <- after you click on the office icon]
3) Click on the "Popular" Section then you should be able to see it has a section called "Peronalize your copy of Microsoft Office"
You should be able to change your User name there.
Please forgive me If I mis-understood your questions.
Chi