I had a nasty problem with Office, I couldn't open documents created in Office 2007 with Office 2003 even after installing & reinstalling the File Format Converter from Microsoft (Compatibility Pack), this happened with Word & Excel. After wasting hours reading lots of posts through the web, deleting normal.dot, then reinstalling office, messing with windows registry, nothing worked. Until out of desperation I checked the services running under Windows XP and found that the service named WebClient was on manual and not running, so I initialised the service and then suddenly all Office files opened and saved flawlessly (2003 & 2007), now I don't know if this service is the only one directly responsible for this behaviour or if additional services need to be running in order for Office to properly open and save documents. But here's the solution that worked for me: Execute services.msc Look for a service called : WebClient Check wether the service is running, if not initialise it, and make sure its default settings are set to Automatic so it starts whenever you start your PC, Click Ok . Now try to open & save Office documents, and see if it works, it did for me. Like most services on WinXP the description for this service is so generic that it almost makes no sense: Enables Windows-based programs to create, access, and modify Internet-based files. If this service is stopped, these functions will not be available. If this service is disabled, any services that explicitly depend on it will fail to start. Hope that helps...