So just got a new PC with gigabyte z97 d3h motherboard, i5 4670k processor and 64-bit Windows 8.1 OS. Had asked the shop to put in 4X2 Kingston Hyperx Fury 1866Mhz RAM and initially I thought that he did it. I usually play games while I work, so loaded up fifa with firefox running in the background. After sometime I exited the game and found a pop up message saying that the computer was running low on memory and I should close firefox. So went to the task manager and checked the RAM and found that the guy had put in 1333Mhz....he has billed me for the same product (so no discrepancies there)...available RAM was around 5.9 to 6GB though in system information screen it says 7.89GB usable. Checked out the product package and entered in the model number and found on Amazon that a couple of guys were complaining the product not working well with 64-bit OS. My question is...is it really so? Should I go to the shop and argue with him to put the 1866MHz RAM or should I simply let it go and there are settings that I can change to extract more from the existing RAM?