I'm definitely no expert on this subject but i did a little testing a while back.
I was under the impression that every motherboad/hdd/dongle had a unique key pairing and basically if you lose 1 piece from either of that then it's dead. Changing HDD/dongle/motherboad from anything but it's original unit from the factory meant it was basically dead (from an original game perspective)
But from my testing that wasn't the case.
I tested a bunch of LOV 4 units and the pairing is motherboard/dongle/hdd/DMAC card. Yes, the dmac cards are also part of the security chain. BUT... you can swap HDD and dongles for the same game between units and they still boot. Now I only did this for LOV as that was all i had multiples of at the same time, but this breaks what I initially thought was the case security wise.
It seems the security was created at the game level, not the unit level. So it's not unique individual keys for everything per unit, it's just per game. I can't confirm for other games, but for LOV it certainly seemed that way. I can confirm that you can't rip a DMAC card out of a Gunslinger and put it in a LOV4 and make it work to boot the original game. There's something in the DMAC card that links it to that game. This includes the ATA HDD lock keys, they have to be the same across the game, otherwise i wouldn't have been able to boot the game across 3 LOV motherboards using the same HDD, it shouldn't have worked if the ATA keys were different.
Can't confirm if this is the same for other games, but it defintiely was for LOV4. But the thing is... most of the games require custom controllers and nesica network access to use, and everything is dumped and stuff is patched out to work on a pc for the most part. So... they are sort of, kind of useless, except for getting a game running, that you can't play without nesica (which doesn't exist anymore) or custom controls anyways.
If you boot your pc with one of those drives connected, your bios should ask you for a password before it will boot. If it doesn't then they're ATA unlocked. If they don't require a password, and they are blank they they are wiped most likely. You won't be able to read any data from them without unlocking them. No idea how to unlock Toshiba drives. WD ones you can find the info easy on google. From my perspective, they are basically useless, except as replacements for pretty unpopular arcade machines that have requirements that you can't meet as the servers were shut down for all the games long ago anyways.
LOV4 requires a special asic (i think) based controller for reading cards as it's a card game, and Gunslinger is an online multiplayer game. I have 1 or 2 for collectible purposes, because they look cool, otherwise i just bin the drives and the dongles!
My 2c.