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@ejn63​ Alienware M18 R2 

Storage support depends on the GPU you have.

Your Alienware m18 R2 supports the following storage configuration:

• Two M.2 2230 and two M.2 2230/2280 solid-state drive slots, for computers shipped with NVIDIA GeForce RTX 4080/4090 graphics card

• Two M.2 2230/22280 solid-state drive slots, for computers shipped with NVIDIA GeForce RTX 4060/4070 graphics card

If you have the 4080 or 4090 GPU, you can add two M.2 2230 drives. 

@ejn63​ I saw already that, I have 4070 GPU but I have two more spaces for that SSD is weird, I just ask why

There are two possibilities -- that the manual is incorrect and those sockets are useable, or that they're there because the same hardware layout is used for both boards, but the sockets have no electrical connection.  You can try installing a drive in one of them -- if it works, you're set, but if not -- the sockets are not active.

@ejn63​ Cheers mate, I will try thanks for your time 

I have seen a few different variants of the Alienware M18 R2 so the only way to be sure is unscrew the bottom and take a look see