How can I switch my Wordpress MU setup from sub-domain to sub-directories?

I've been working on getting my online community switched over from Ning and I've been diligently working at it however I've hit a snag. I thought it would be good to have my users blog address be name.domain.com, however, it doesn't look like my server doesn't support a wildcard, as well as, I'm looking to forward a domain to this wordpress and I don't want my users to have my URL in their address...I want the one that I'm forwarding to be their main address/domain.

Basically, I was wondering if there's any way for me to switch my install from sub-domain to sub-directories without losing all the work I've put into my wordpress ... so far.

Thanks everyone!