Can I replace the HDD that's inside of a WD My Passport?

I need to buy a new HDD drive for my laptop and I want to keep my current HDD as backup.
Is it a good idea to buy an external My Passport model, open it and replace it’s HDD with my old one? I know that I will void the guarantee.

Does a Blue internal HDD have more performance than the HDD inside My Passport?
Can I put another HDD in a WD My Passport shell?

Hi rostamiani,

WD My Passport is an external drive and it cannot be used as an internal drive.

For which purpose you want to purchase the drive? As different drives have different specifications and purpose.