Thanks for that, SD.
Yes, both hard drives are SATA and the optical drives are on the primary IDE channel. I've had a delve and changed them over to the secondary channel but to no effect. In the BIOS, primary channel devices were noted as 'not detected' (having effected the change to IDE 2). I take it that qualifies as setting them to 'not present' as you advise?
Don't bust a gut over it, but if you have any other ideas I'd be pleased to hear from you again.
Ta
N o t a