Global File Associations

How does one go about changing file associations for file types for all users? I've recently installed iWork '08 on a computer on the network and now when I log in as a user it wants to open all of my Excel and Word Documents in Numbers and Pages respectively. How can I get it to default back to Microsoft Office for all of my Microsoft Office documents for all users. The iWork '08 install seemed to just take over, so it must be possible. Thanks! Chad