I have put 2 x 1bg ram sticks into my computer. Both exactly the same e.g. same speed, same type so I could have dual channel but windows is only recognising that I have only 1 stick installed, whereas cpu-z is finding both sticks. Also when I use balerc it says I have 1024mb in slot A0 and I have 512mb in slot A1. I don't understand this at all!

Try to update the bios

Install 1 stick only. How much ram is reported? Remove it, and install the other stick how much ram is reported?

For dual channel on most boards, you need to insert the matching pair into the matching colored slots (i.e. Blue slots for dual channel).