cannot lock partition

I am trying to change the volume label of drive D:, which is a primary,
non-system partition (Basic disk) on my hard disk. Drive D contains ONLY
data, no executable programs.
I have administrative rights.
When I try to change the volume label using disk management, I get a message
I do not have the rights to do this.
When I try doing it in Partition Magic, I get the error message it cannot do
it because it cannot lock the partition.
I've tried to close all other programs: used msconfig to disable all
startup and rebooted, but get the same message. Any suggestions of what I
need to do to make the disk lockable?