Unfortunately, there is no GPO setting to disable the Word Options button in the Office 2007 GPO templates. you need to create a custom Word document template with the options button disabled and then place it at one of the following locations (depending on Windows version):
C:\Documents and Settings\username\Application Data\Microsoft\Word\STARTUP
If the computer is a terminal server or if it is otherwise used by multiple users you can also place the template at the following location:
C:\Program Files\Microsoft Office\Office12\STARTUP
I have some lines of code that will show you how to do it, but I can't post them. If someone can tell me how to post them I'll gladly add them to this answer.