After reloading Windows 7, cannot connect to server network

We had a hard drive fail on a Windows 7 Dell Optiplex 380. Dell replaced the hard drive and we reloaded everything on the computer and thought we reconnected it to the the LAN network on the server. Instead, it created network 2 to join the LAN. It shows up in the client machines on the server. It connects to email through the exchange server. It does everything it is supposed to do except connect to the common database files for Quick Books and Peachtree on our server. It rejects connecting to the local WAN. The error message is that it is unable to join the network. Any ideas on how to fix this?