LOCK/UNLOCK A DRIVE

I have a pentium 166 mhz computer which I am trying to partition using fdisk.exe. During the operation it tells me the partion cannot be changed because the dive cannot be locked. So I use the Lock command to lock the drive and it goes through the process and even asks me if I am sure I want to do this. When I type Y for yes I get a message that says ” Lock Operation Failed”. Can someone help me

Thank You