I put in a big order at cdnow with instock stuff and prorders spread between now and May. They shipped one instock DVD but have the rest of the instcok discs as PROCESSING(being held until rest is in stock so it can all ship at once) is there any hope they will ship more discs as they come in stock or will I really have to wait until my last preorder in May before they ship the rest?

You will have to wait. They used to ship everything as it became available, but as of last October, they no longer do more than two shipments. Since they already sent you one shipment, everything else on your order will be held for the second.

I also got caught by this new policy last October and since then have been very date cautious on my orders and usually try to have no more than two different release dates in a single order. I did an order in January that had three release dates and, sure enough, got caught again when one of the street dates got bumped by several weeks.