The Office HTML Viewer server provides support for users who want to view the content of files in Microsoft Windows SharePoint Services document libraries, but do not have Word, Excel, or PowerPoint from Office 97, or a newer release of Office, installed on their local computer.

http://www.microsoft.com/downloads/details.aspx?FamilyID=c62e0232-9bf6-48fc-829e-5c34d5c8b15f&DisplayLang=en