Using Process Explorer I discovered what process is keeping the file locked. I discovered that the drive that I mounted my file to remains still locked by "clmlSvc.exe" and preventing dismounting. I discovered "clmlSvc.exe" is owned by CyberLink MediaLibray Service. I believe that is the CD writing application pre-installed on this pc.
Armed with that knowledge what should I do? I do not want to have to manually stop "clmlSvc.exe" every time I want to unlock a TrueCrypt volume.
[Incidentally I tried to use "Unlocker.exe" to discover what was locking the file but it does not seem to work correctly in W 7. At least it does not appear on the right mouse click contents. Is there a trick to making it work in W 7?]
Thanks for any help.