NT Net login Service won’t start

The error message that I am receiving is referred to in TechNet, q234655, which states, “unable to log you on because the Netlogon service is not running.” The fix is to install service pack 6a but I can not log onto the server to install the service pack. Steps to error message, the server locked up and I lost the boot record. Next, Modified the boot ini so repair could be preformed. Any suggestions? My next step is to replace the SAM file through a client on the network. I can not afford to loose any data on this machine!