Before anything I'm running windows 7 64 bit ultimate. So basically most of my ram died and I was left with 4 GB of apacer 1333mhz Ram out of 12GB, so I found my old adata 2 GB 1066MHz ram and I put it my PC, in the Bios it says that it detects it and both memory sticks run at the same latencies(I could be wrong though, but the numbers on both were the same) and at 1066MHz(due to the adata being slower) and when I go to windows and Computer/properties it says that I have 6.00GB ram, but only 3.96GB is usable.