Thank you for the quick answer and i am sorry for the way i wrote the 2X(2GB).I meant that i have 2 X 2GB=4GB Ram and now i also found SIV32L-System information viewer that say Maximum capacity 8GB, 2 devices with No correction so now i am going for 64 Bit OS.I just needed to be shore that i can't install ddr3 into ddr2 slot's(now it is fearly obvious)and that 64 Bit OS can be installed which you experts also confirmed.Thank you for all your help.