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Thank you both. Yes, we did power up the second drive with a spare Molex connector dodgyshirt and no offence taken.
It was an old BIOS (one of the older HP Pavilions from the mid ninetees).Oddly, on checking the Pavilion's own drive, there was no cable select option available according to the diagram on the back of the drive. To complicate matters further, the 30Gb drive was a Western Digital Caviar with "Master", "Slave and "Single" but again no cable select.
We went out this afternoon and bought an Akasa HDD drive enclosure from PC World. It cost about �25.
We installed the 30Gb drive in the caddy, installed Akasa drivers etc off the CD and powered it all up after cabling it all together.
The 30Gb drive was there in My Computer with a new drive letter assigned to it. We then copied off what we needed and formatted the 30Gb drive.
It all worked like a dream. I can't get over how simple the solution was to something that's caused me quite a few sleepless nights. The Akasa is always handy if I ever need to back up another drive in the future.
Thank you both very much for you help. It's very much appreciated!