Everyone's nightmare, bad luck!
You've probably thought of this but have you checked the jumper settings for slave and also the cable integrity? Try another cable or the other IDE interface.
Forget booting from it, the data will probably still be there if you can only get at it.
Otherwise my only similar experience with a serviceable HD that wouldn't function in other PCs was that it could only be seen by the same old HP BIOS in the PC where the HD was originally formatted and used. It, too, was a 4.3GB Fujitsu.
That's all I can think of. All the Best!