inherited problem

Hello all,
I'm hoping that one of you can help. I have an OWA site using SSL, this
works no problem. The problem is that the SSL cert has been issued to the
wrong domain, this company used to be xx.com now it is yy.com. I have no
clue as to what the previous admin did, but I'm stuck cleaning it up. If I
go to directory security for OWA, I can view the cert, but the server
certificate button is greyed out. I can set up a new cert via the
certificate server, but how do I remove this cert from OWA? Do I revoke it
from the cert authority or ?? To make it even more strange, if I look at
the properties for the default website, it has a different cert than the one
being used by OWA. Any advice would be appreciated.