How to restore MBR

After installing Service Pack 4 for Win 2K, i could not access my secondary hard drive even though the system has detected it. As soon as i click the secondary hard drive icon in ‘my computer’ a message saying the hard drive is not formatted and asked me if i wish to format it.
Not too sure what went wrong, but my guess is probably got to do with the MBR. Is there any way to restore it or could it be something else?