The Office 2010 Office Customization Tool (OCT) can add and remove files to/from a computer that is installing Office. These are the steps in the OCT where you can add and remove files:

Notice the text in the Add files step; Specify files to add to the user’s computer during installation. When you exit this tool, copies of the files are saved in the Setup customization file. Notice also the Location column; [AppDataFolder]Microsoft…

So in the example above the normal.dotm and Word.officeUI files will be added to the MSP (Windows Install Patch) file.

When you deploy Office to a computer the files are copied from the MSP file into the [INSTALLLOCATION]Microsoft OfficePatchFiles and renamed with GUIDs as their names:

Now, looking back at the Location column in the Add files step in the OCT we can see that the files in this example are to be copied into the [AppDataFolder]Microsoft… etc. A user’s AppData folder is stored in the %APPDATA% environment variable and it’s usually something like: c:Users%username%AppDataRoaming. But since all users who log on to the computer, not just the one installing Office, needs these files they are copied from the PatchFiles folder into the AppDataRoaming folder for each new user who starts one of the Office applications. This feature also works the same way when Office is installed by the SYSTEM account, and not a user; the files are copied from the MSP file into the PatchFiles folder and from there to the user’s AppData folder.