win2k does not finish loading

after blowing my exchange server, which is also the domain controller of dust, i tried restarting it. however, when it got to the screen where it’s supposed to say windows is starting up and preparing network connections, only a cursor showed on screen and it hung there. i booted from safe mode to install service pack 2, so that any missing or corrupt files could be reinstalled, but the service pack would not install. the error message was rpc server unavailable. i then booted from cd and used the repair feature to reinstall win2k. after finishing and re-booting, i was able to go into the login screen and logon. however, this is where windows stops loading, so i cannot see the desktop. as a result, users are able to log into the network but exchange 2000 is not running, as service pack 2 is not installed. how do i resolve this.