As far as I know the My Books all just use SATA drives, so there shouldn’t be any problem there. You will probably need to format the drives when you move them to the PC though.
How are you planning on setting them up, are you planning on doing any raid with the 2tb drives?
SATA doesn’t have any slave/master system like PATA.
I don’t relaly know if you should open those enclosures and move them to a desktop, the drives themselves should work but you will still need backups. As far as I know WD bin their drives/drive components, and the external products get the lower end of the pick i.e. not all drives are made equal, they are tested and the lower quality ones go into the external products. I heard then it goes consumer drives, them OEM drives (like Dell). Of course, WD are never going to confirm this and it’s really just hear-say. It really just depends on how important the data is you you, if it’s worth getting a new drive and using your existing external ones to backup.
Also, you lose your warranty if you open the enclosures, so assuming they are out of warranty they are aging a bit anyway.
You can extract the drives and put them on a standard SATA interface, but say goodbye to the data on them if the drive allows for password encryption (even if your password is blank).
For most of the external drives, you’ll want to insert a wedge at the top front of the drive casing (centre) between the 2 pieces of plastic and pry towards the rear.
Using a plastic case opening tool preferably, inset the tool at the top rear of the drive (either side) and slide from top to bottom, and then do the other side, keeping pressure at the top front pushing the 2 casings apart.
Flip the drive over top-to-bottom, and repeat prying the bottom towards the rear of the drive, and unlatching the rear.
the 2 halves should just slide apart. Put the front to the right, and rear to the left, and slide the 2 halves left and right until they disengage.
The rest of the disassembly should be pretty evident by looking inside and figuring out which way to push the rubber mounts to disengage the drive from the casing. If there is a plasic optic bringing the activity light to the front, take that out first. It should slide out towarde the front (the long way - the whole thing has to go thorugh the hile, you can’t just pop it out going backwards).
The drives will need to be partitioned and formatted before you can use them.
In some cases, depending on your system, you may need to manually assign the drive letter.