Lenovo ThinkCentre M73 10B6001SUS Desktop Computer - Intel Core i5 i5-4590 3.30 GHz, Small Form Factor, Business Black 3.3GHz Intel Core i5-4590 Quad-Core Processor (4 threads, 6MB cache); Intel HD Graphics 4600 4GB (16GB Max) DDR3-1600 SDRAM, 500GB 7200rpm SATA 6.0Gb/s Hard Drive, DVD-Writer 2 x USB 3.0, 4 x USB 2.0, Serial, VGA, RJ-45, DisplayPort, 2 x PS/2 Gigabit Ethernet, High Definition (HD) Audio, Internal Speaker (1 Watt), USB Keyboard and USB Optical Mouse Windows 7 Professional 64-bit pre-installed (Upgradeable to Windows 8.1 Pro 64-bit)