CSI Dark Motive DS help plz?

I'm stuck with the evidence ive collected. I've some how managed to put a fingerprint in the lab computer for ysis but i cant get swobs into the computer or the microscope. What do I do? I've tried to give it to greg but nothing is happening. And the dust next to the bin in the crime scene i can't get anything from. And the ramp where the tire mark is, what evidence can I get from there? Plz help. I love this game but I cant get any further now :(