Exchange 2000 OWA

This will be a very long process, hence the high number of points for sticking it out.
I have a Win 2000 Exchange Domain controller with Exchange 2000 behind a firewall. I would like to be able to get OWA going on it. BTW: I also, regretfully, have run the IIS lockdown tool on it.
When it try to check it, it gives a error “HTTP 500 – Internal Server Error” My problem may be anything from the lockdown tool to the firewall to the setup not being right.

Thanks,
David