Does a Hard Drive have to be exactly the same?

[merdoc3]

This is concerning a Maxtor Mini 320GB hard drive where the actual disk drive is a seagate Momentus 5400.5 320GB Hard Drive, st9320320AS. Recently my external hard drive failed. I can hear the drive spinning but the PC doesn't recognize it (WIndows, Linux, mac). Computer management displays the drive as Disk #: unknown and not initialized. I don't want to initialize the drive for fear that my data will be wiped. When I go into Device manager, the drive capacity is displayed as 0mb. When I run Disk Internals, I get something different such as 2TB. Strange. Either way, my every instinct point to a bad/corrupted firmware where my initial thought process has led me to conclude that the answer is to replace the PCB (I think I got that right). I've only done this once with success. However that was years ago. My only question is how much of an identical board does the pcb have to be? Can the Model, Serial Number, and Part Number be different as long as the Firmware is the same? Or does everything have to line up perfectly? The problem I'm having is that I cannot find the pcb I need that fits all the numbers perfectly (SN, PN, FM). I found one that meets the SN and the firmware, but nothing else. Then I found one that was made for the seagate momentus 5400.5 (which is what I have), however the SN, PN were different but the firmware was the same. Then I found another 320GB HDD that is identical to mine in every way, except the pcb boards--for example I found one that is a 320GB 5400.5 RPM ST9320320AS. Is there any wiggle room here or should I pay to have it sent to the experts and let them deal with it?
Let me know if you need additional detail.
Thanks...

 

[sminlal]

A lot of modern hard drives store critical operating characteristics of the platters in a flash memory chip on the controller board. Even if you manage to find an identical model made in the same batch as your failing drive, simply swapping the PCB may not work because those characteristics can be unique to each set of platters.

The best defense against these kinds of problems is backups...

 

[inzone]

If you go into Disk Management and you hdd is listed there with no drive letter then it may need to be initialized , if it hasn't been initialized then there is no data on it because to store data on it the drive needs to be initialized and a drive letter assigned to it. Initializing a hdd creates a partition and untill you do that it is a raw partition and there is no structure to it.
Before you go too far if you feel there is still data on there then you need to try and recover it with a software peogram like this one;

http://www.cgsecurity.org/wiki/TestDisk

Becqause even if you do find your pcb that matches you will still have to initialize the hdd to use it.