Lenovo ThinkPad E540 20C600AAUS 15.6-Inch Laptop (Black) 2.40GHz i3-4000M Dual Core Processor (3MB Cache, 1600MHz) provides power to handle all your computing tasks Windows 7 Professional 64 comes installed offering a user-friendly environment to work on with the option of installing Windows 8.1 Professional at no charge if desired later. 15.6-inch HD (1366x768) LED-backlit display delivers clear visuals | Optical drive: DVD+/-RW SuperMulti Drive (reads and burns CDs and DVDS) Speedy 7200 rpm 500GB Hard Drive: Dont settle for the slower 5400 rpm on many competing models | 4GB DDR3 memory 802.11a/b/g/n wireless internet support and Bluetooth 4.0 | Full-size Keyboard with 10-key numeric keypad | 6-cell batty offering up to 6 hours battery life Intel Core i3-4000M processor, 2 cores, 2.40GHz, 3MB cache 6GB max, PC3-12800 1600MHz DDR3L, non-parity, dual-channel capable, two 204-pin SO-DIMM sockets 500 GB 7200 rpm Hard Drive 15.6-Inch Screen, Intel HD Graphics 4600 Windows 8 Professional, 6.2-hour battery life;Windows 7 Professional (64-bit)This version of Windows 7 Professional is preinstalled through the downgrade rights in Windows 8 Pro (64-bit).