registry cannot load hive file

hi, i am using windows 2000 advanced server on ntfs. I recently tried to install service pack2 on that.after installation, i rebooted the system. It is coming up with the stop message during the start up.The message is as below;

The registry cannot load hive file. systemroot/system/config/software.
It is absent or corrupt.

I used the recovery console from the 2000 cd and did rename the config to config.old
and then copy the config.old to config again. But No Use . Its showing the same message.

Is there any other way of fixing it other than formatting and reinstall the 2000(I really cant do this as i loose data).
Please give me suggestions.
Thanks