How do I fix this?

I hope someone can shed some light on this for me. I was installing a new exchange 5.5 server into my site and everything went fine. While installing Exch SP4, the installation was interrupted and was cancelled at approx. 50% complete. Now when I try to re-run the SP installation, it wont work. It gives me some weird error and doesn't let me install it. Even worse, none of the Exch. Services are able to start. has anyone run into a problem like this? If so, how is it that I can remove this server and start over without it having any serious impact on the rest of the site? There are no users on the server or connectors installed either. Any help would be appreciated.