There are more than one valid reasons for doing this. In one case, a company buys out another company. The assets exchange possession and you want to re brand the applications to reflect company ownership. Here is how.

Using regedit, edit the registry for the following keys. Be certain that there is a 00 between each letter.

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\Office.0\Common\UserInfo]
"UserName"=hex:56,00,61,00,6c,00,75,00,65,00,64,00,20,00,43,00,75,00,73,00,74,\
00,6f,00,6d,00,65,00,72,00,00,00
"UserInitials"=hex:56,00,43,00,00,00
"Company"=hex:56,00,61,00,6c,00,75,00,65,00,64,00,20,00,4f,00,72,00,67,00,61,\
00,6e,00,69,00,7a,00,61,00,74,00,69,00,6f,00,6e,00,00,00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Installer\UserData\S-1-5-18\Products40110900063D11C8EF10054038389C\InstallProperties]
"RegOwner"="Valued Customer"
"RegCompany"="Valued Organization"