Cisco PIX, Please Help Me

I just took over a new network and just implemented a new Small
Business Server 2003 with Exchange. The old NT 4.0 server is still on
the network with exchange 5.5 disabled. I cannot access OWA on the new
server because the Cisco Firewall is NATing to the old server IP
address. I have never used a pix firewall and therefore i have no idea
how to change the configuration. I beleive the firewall ..
Telecom, Cabling and VoIP continues...