does this mean that I dont have dual channel? as i got 2X256 and 2X512 in my pc, giving me 1536mb of ram.... In what i thought was dual channel.
no it's not running dual channel.
Download CPU-Z from www.cpuid.com
and in the MEMORY tab it will tell you that your RAM is running in Single channel mode
DC is achieved by 2 sticks of the same speed and specs, and sometimes although not always, 2x256 in slots 1&2 and then a identicle 512mb stick in slot 3