NAT won’t share?

Please bare with me. SOHO network using Windows 2003 SBS as it’s main server. Active Directory,domain controller,etc. Windows 2000 Advance is member server with ADSL installed and connected. Two NIC’s for public and private interface. Private IP: 192.168.X.X. Enabled RRAS and NAT(LAN only). Instructions said to activate the DHCP allocator and DNS proxy on the NAT if I have DHCP on the LAN. Event logs says allocator shutdown because of two DHCP’s on same network. Un-check automatic IP addressing and client resolution and still nothing. Now suddenly, the modem itself sent a DHCPNACK meesage and no DSL? HelP! What am I obviously doing wrong?? Thanks alot in advance…..very troubled..:-(