The Dell Alienware 18 R1 Laptop Supports up to 4 Drives. (Two 2.5" Solid State Drives or Hard Drives in the Internal Bays and One 2.5" Drive in the Optical Drive Bay and One mSATA Solid State Drive in the Internal mSATA Slot) Note: The third 2.5" Drive is optional and is located in the optical drive bay when Installed. If replacing the optical drive for the third 2.5" Drive, you will need the Dell optical drive bracket p/n RJF2Y and the optical bay drive cable p/n R64M2 for installation.