@Davet50: BIOS should recognize all 4 sticks, Win7 will recognize only 3.25 GB.
@Soruind: I checked your picture, it is weird. Confirm my understanding, you moved RAM sticks around, so it cannot be defective RAM, correct?
The only thing comes to mind is to clear CMOS - you would have to turn off PC, open side panel, ground yourself, find round shiny object (motherboard battery), pay attention how it is installed, next remove it for at least 15-20 minutes, then place back, and see if it helps. Do this procedure first with all RAM installed, if it doesn't help, remove all RAM, 20 minutes, place battery back, and place all RAM back. If no help after this, I am afraid that motherboard cooked. If you have chance to return RAM, do so and get 2 GB sticks.