dual channel ram installation QUESTION

I have 2 - 512 sticks of ram and 1 - 1 gig stick of ram ... the motherboard runs dual channel and I'm not sure how these should be installed ....
on the motherboard there is 4 slots for ram ....
blue, black - blue black

how should these sticks of ram go in ... could someone please help me out and tell me which colour slots these sticks of ram should go in ...

thank you so much !

For dual channel ram you install two identical modules in the blue slots. If you add the extra 1gig stick that will knock out the dual channel capability. So, either use the two 512 as dual channel, or lose your dual channel and use all three modules. Or better yet, get two 1gig sticks, and sell the two 512s.