unclip the memory sticks from the motherboard, take them out, clean the contacts.
*edit* brush everything with an old toothbrush to get rid of dust and rubbish!
plug them back in until the clips click shut.
try to boot the pc again.
i'm off to bed now as it's 1:06am in england.
if you have further problems or need more advice, post and i'm sure someone can help you.
good luck and good night.