I've just noticed this one dropping off page 2 of the forum, so here we go:
You don't say whether you are using dynamic pages to load your documents. Any intranet is normally far better off written in ASP, PHP or .NET.
If we assume you are using ASP, to load your documents properly you need to change the MIME Type or Response.ContentType in your ASP page, which allows the Word or Excel file to be opened directly in the browser and saved as Word or Excel formats from the browser itself.
There are a lot of pros and cons to consider, and the above is not necessarily a solution to document sharing, but it does (hopefully) set you on the right path to being able to open the files into the browser.