Things to try:
In the registry: HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Common\UserInfo
It seems binary coded: my name Kees is represented as 4b 00 65 00 65 00 73 00 00 00, which you'll able to make sense of using http://www.asciitable.com/ This seems where Office keeps it. There's a copy for each user, of course.
Also in the registry:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion as shown in http://www.pctools.com/guides/registry/detail/32/
This is where Windows stores it.
In your case of MS Word keeping old information, I'd start with finding normal.dot (the default template) and delete that. Word will make a new one, and my guess is that it will contain the info from the first registry location I specified above.
I have a very strange problem - made worse by lack of documentation by Microsoft. I am puzzled by the entry for "Company" that always appears under File | Properties. It's the same OLD company name that appeared - as a "default" for Organization - when I installed Office 2003. That was mystery enough (where did it get THAT name from?!?) I have heard that "Word will default to the registered name of the computer." That might explain how Word displayed my OLD company name during install. But since it let me revise that name before clicking Next in the install series, why does it reappear now? (It ignored what I entered!)
When I came to that screen, I changed that company name (field is Organization) to my current one. Unfortunately, when I now load up a blank Word document, and then do File | Properties, it displays the OLD company name - not the one I supplied on install. Where is MS Word getting this OLD information and what can I do to regain control over the File Properties details??
BTW, I'm running Windows XP Pro.
Very puzzled & frustrated.