I'm working on a project with 2 sites connected by a VPN. Site 1 has the main server and there is a secondary server at site 2 which I am trying to replace. The current setup works perfectly however I can't for the life of me get the replacement server at site 2 up and running. I'm trying to replace like for like just upgraded hardware.

I have installed the OS (all Server 2003 Standard SP2) and used exactly the same settings as the old server. I have setup Active Directory, DNS Server, DHCP Server and WINS Server configured. I have used all the same settings as the old server (except IP address and name). I can access the active directory but I can't do anything; add, edit, delete all returns "the directory service is unavaliable". No-one can login on any of the computers on site 2 and the internet is down. Plugging the old server back in and connecting it to the network rectifies the issue (so both new and old are connected at site 2), everyone can login and the internet is back (curious since the modem connects direct to the switch, and even with the new server online I can connect to the router via IP but not the net).

I really don't have much experience but I've been roped into doing this because my company is too cheap to hire a real network admin. Any suggestions of where I can start to troubleshoot this, its driving me crazy and I only have a day before all the users are back on site.