The HP Elite 8300 SFF Small Form Factor Business Desktop Computer, Intel Quad-Core i7-3770 3.4 Ghz- to-3.9 Ghz turbo came with WINDOWS 10 PRO-THIS OPERATING SYSTEM IF YOU WANT TO BUY IT SEPARATELY COST BETWEEN $129-$149 AND add on for me 8 1/4 NY STATE tax. The Intel Quad-Core i7-3770 can be purchased between $100-$125 used and new averaged at $225 AND add on your STATE. I took a chance because I got a great deal at Amazon for $228 and tax $250.36 TOTAL. The computer is working great even though it came with only 8 gigs (2X4 sticks) of ddr3 (1600) memory from MICRON. I added 16 gigs (2x8 STICKS) CORSAIR VENGENCE PRO BRAND. PAY PARTICULAR ATTENTION: The Corsairs ddr3 (1600) COME WITH HEAT SINKS. THERE ARE 4 MEMORY SLOTS ON THE MOTHERBOARD. UNFORTUNATELY (FOR THE MOMENT) THE HEAT SINKS ON THE CORSAIRS PREVENTED THE COMPUTER LID FROM CLOSING. THE PROBLEM WAS EASY TO FIX. THE POWER SUPPLY SLIDES UP OR DOWN TO THE CLOSED POSITION BUT ONE OF THE CORSAIRS HEAT SINKS WERE TOO TALL AND PREVENTED THE POWER SUPPY FROM LOCKING INTO POSITION. THUS PREVENTING THE COMPUTER LID TO CLOSE AND LOCK AS WELL. I resolved this by moving the CORSAIRS to the next set of remaining 2 slots and putting back the original 8 gigs (2X4 sticks) THE WAY IT CAME and it closed nicely.  OVERALL: the computer came clean, dustless and extremely well packaged-I kid you not! APPARENTLY the computer was very well PLASTIC wrapped and taped and placed in a box with QUICK DRYING INSTANT FOAM. MORE INSTANT FOAM WAS ADDED ON TOP ALL THE WAY UP TO THE BOX BORDER-REALLY EXCELLENT WORK. The computer came with a key board and a mouse and that was that! *****PLEASE NOTE***** IF you want to add a nice graphics card make sure it too is small (low) factor FORM (FOR THOSE WHO DO NOT KNOW-IT'S A SMALLER SLIMLINED GRAPHICS CARD) or the GRAPHICS CARD WILL NOT FIT. OTHERWISE THE COMPUTER IS EXCELLENT FOR THE MONEY ($250). I don't work or get money from AMAZON. I can only to the best of my ability give you an honest assessment of the refurbished  HP Elite 8300 SFF Small Form Factor Business Desktop Computer, Intel Quad-Core i7-37 I purchased from AMAZON. DO THE RESEARCH MOST ARE INTEL i5'S WITH MORE MEMORY OR FOR MORE MONEY AN INTEL I7 BUT WITH LESS MEMORY. ALSO KEEP IN MIND WHEN THE COMPUTER IS LISTED AS A SMALL OR LOW FACTOR FORM; WHATEVER COMPONENT FITS IN A SMALL, MEDIUM OR LARGE TOWER MAY NOT FIT IN A COMPACT SMALL OR LOW FACTOR FORM DESKTOP-DO YOUR RESEARCH