G.Skill send us a 4GB DDR2 kit, while installing 4GB seems to be a problem in Vista and on some motherboards I have’nt had any trouble at all. I used Windows Vista HP 64-bit seeing Vista 32-bit is’nt able to adress the full 4GB of memory. But I have tested these modules with Vista HP 32-bit as well and they worked just fine, but I had to with 3,5GB instead of the full 4GB. Wanna know more read on.