Locked drive - Defrag won't run

Help guys! I've searched on this one but haven't had any luck. "Windows cannot defragment this drive now because it has been locked by a disk utility. Quit any utilities that may have locked this drive, then try defragmenting this drive again. IDNO: DEFRAG00105". There is nothing running before it starts except Explorer and Systray. What am I missing here?
Thanks, Reg

I've seen this sometimes I don't know why it happens.

There is an unlock switch in your computer.

Why its locked I couldn't tell you.

Run this command at a dos prompt:

"lock c:\"

It will then ask if you want to unlock this drive for full access. Answer yes and you should be good.

.JL.