The LS dignostics don't indicate a problem, but with the media 'upside down' in the drive the drive is locked/dead, even explorer stalls.  Do I have a software conflict - if so where to start looking?  Otherwise, I wonder if our company AV software has locked the drive until it has checked the disk, but, with nothing to read it never completes. Is the chuntering sound the disk hunting for a directory?  Aternatively, could it be that the drive LS detection mechinism is broken?  

The Laptop is an HP/Compac NC8340 and the drive is the standard TSSTcorp CD/DVDW  TSl632M (0917 127)

Any other ideas ... anyone. 

One thing to try would be to see if it makes the same noise with a AV Disk.

Usually, drives make more of a "stepping" or "dragging" noise as the heads are moved over the disk.  It usually starts as soon as the disk is mounted trying to detect the media.

It's hard to tell without actually hearing the noise!

I assume you also tried another disk & from what you describe the disk was reseated the disk.  Drives can make a "grinding" noise if the disk isn't mounted correctly.

I use an HP Pavillion dv9825nr that has a similar drive number.

Also, if you can, try manually ejecting the disk.  This can be done by bending a large paper clip so you get a straight piece of it sticking out & gently push it in the small hole on the front of the tray.  This might make the system "unfreeze" & recover.

Be sure to do this when the activity light goes out or at least is out.