Describe your threadI installed 24gig DDR3 RAM when I built my pc, with Win 7 Home Premium. I noticed that it was only using 16gig of the 24gig I installed, which was the maximum Home Premium could use......... however if you upgrade to Ultimate it will use all of your 24gig RAM......stated the Microsoft rep.............well I upgraded and still only using 16gig.....thanks for any help.