Both DVD Drives Gone 'Missing' - Dimension 5100

I have been reading various posts about missing DVD/CD drives.  Mine do not appear any longer in windows explorer.  I have 2 bootable hard disks and I tried to see if the DVD drives were visible booting from my 'backup' hard disk.  They weren't - so I wasn't surprised that clearing the upper and lower filters in the registry had no affect.

 

I was more hopeful with clearing the NVRAM.  I followed the instructions : Restart : F2 : Maintenance : Load Defaults : Continue.  Still nothing.  In setup I then switched PATA-0 and PATA-1 on (they defaulted to OFF and I am assuming these are the 2 DVD drives) and the booted at which point it said 'Drive 2 (and 3) not  found : Parallel ...PATA-0 (1)).

 

I have disconnected the drive cable from the motherboard and reseated it.

 

I am running out of ideas!  Can anyone help?  Please!