Data Recovery

OK, never tried this so I am a newbie here. I have a HDD that refuses to be recognized by bios or windows. The drive spins when I start up the PC (for quite a while) with boot sequence stopped till the drive stops spinning. Boot then proceeds either showing no operating system/no fixed disk, or just booting up to the primary drive, and not "seeing" the drive in Windows, depending on whether the bad drive is solo or slaved. Starting with a boot disk and attempting FDISK shows no fixed disk. I know I can remove the circuit board from the HDD, but my big question is....do I have to replace it with the exact same board from the exact same drive? I started searching for the exact same drive around here as a tech in a local shop assured me it would only work with the exact piece down to the same rev number. Is this right?
The drive in question is a Quantum fireball plus KX 20.5AT with a part number KX20A011 Rev 01-B

From your description I agree that everything points to logic board failure on the HDD.

You can swap the logic board but it must be exactly the right one, from an identical drive. It is unlikely that you will be able to order a replacement from the manufacturer.

We had to do this loads of times during the "Fujitsu" period a couple of years back (loads of logic boards failing on their 16 gig drives!) - so it does work.

You do need to take very careful precautions against static damage though - the boards are extremely vulnerable to this.

Have fun!;)