OS Provided - Microsoft Windows 7 Professional 64-bit Edition / Windows 8.1 Pro - pre-installed: Windows 7Processor - 1 x Intel Core i5 (4th Gen) 4460 / 3.2 GHz ( 3.4 GHz ) ( Quad-Core )RAM - 4 GB (installed) / 16 GB (max) - DDR3 SDRAM - non-ECC - 1600 MHz - PC3-12800Hard Drive - 1 x 500 GB - SATA 6Gb/sCache Memory - 6 MB L3 Cache