The Dell Latitude E6400 ATG Laptop Supports Single and Dual Drive Configurations. (One 2.5" Solid State Drive or Hard Drive in the Internal Primary Bay and One 2.5" Solid State Drive or Hard Drive in the Removable E-Modular Bay) Note: The second 2.5" Drive is optional and is located in the optical drive bay when Installed. If replacing the optical drive for a second 2.5" Drive, you will need the Dell E-Modular Bay Drive Carrier for installation.