Hi all so iv'e tried to install two sticks of memory into my pc that has two 4gig existing sticks already. The two i'm trying to install are only 2gig each so i'll have a total of 12gigs . Problem is windows won't start unless i take them out. Their make is 2GB 1RX8. I took them from an old work computer that was destined tobe thrown out. Is it that these two sticks are not compatible with the motherboard?