Mike,
You use a COM DLL without registering it.
Rick Strahl has good explanation here. http://www.west-wind.com/wconnect/weblog/ShowEntry.blog?id=890
Doug Hennig pointed to the article in his white paper I found through Google
http://doughennig.com/papers/Pub/Deploying.pdf
It also has a link to Craig Boyd's site with similar information.
Tracy Pearson PowerChurch Software