I have a C# 2.0 (WinForms) project in which I try to activate word 2003 (word is installed on the system). By using the following code:
private void Activate
If it is a permissions problem, and you can't get Sitecore to run as a user with sufficient permissions, perhaps you could write a different service ("WordService") for your Sitecore application to send requests to. Then WordService could run as a slightly more privileged user, do your stuff with Word, then e.g. write the filled-in Word file to a known location SiteCore can access, or whatever you want it to do.