I assume since this is a Network/MU related question it goes in this forum, if not please excuse my ignorance.
I've got several WP installs and planning several more (all using subdomains XYZ.mydomain.com) and I am thinking it would be easier right now to consolidate them under one MU style installation. The only thing holding me back is whether I can still use mydomain.com for the core site. Is this possible?