The Acer Aspire R3-131T Laptop comes in 3 Different Drive Options from Acer and Supports Single and Dual Drive Configurations. (One 2.5" Solid State Drive or Hard Drive) or (One eMMC Solid State Flash Drive) or (One 2.5" Solid State Drive or Hard Drive and/or One eMMC Solid State Flash Drive) Note: Models equipped with a 2.5" Drive are upgradable. Models equipped with a eMMC Flash Drive are not, the eMMC Flash Drive is integrated on the system board and is not upgradable. Select models that have just the eMMC Flash Drive installed do have a additional empty 2.5" Drive bay. If installing a 2.5" Drive, you will need the 2.5" Drive caddy and cable. (The operating system "Windows" is Installed on the eMMC Flash Drive when present)