Name and Company Information (after installation of Windows XP) can be changed in the Registry.
Follow the Microsoft instructions:
Click Start, and then click Run.
In the Open box, type regedit, and then click OK.
Locate the following registry key:
To change the company name, do the following:
In the right pane, double-click RegisteredOrganization. Under Value data, type the name that you want, and then click OK.
To change the name of the registered owner, do the following:
In the right pane, double-click RegisteredOwner. Under Value data, type the name that you want, and then click OK.
Click Exit on the File menu to quit Registry Editor.
source: Microsoft Support Website