HP OmniBook 5700CT HDD

The 2Gig 2.5″ Toshiba HDD used by HP in this LapTop has suffered a head crash. Is it unique in some way?
I have tried to replace it with an IBM 10Gig HDD but the BIOS refuses to recognise it correctly in the main SCU window, even tho it Auto detects it correctly.
When trying to Fdisk it, Fdisk says there is no HDD installed. I’m stumped.

HP want the earth for any advice or assistance & even more (A$700) for a replacement 2gig drive.