@Tech: OK i see i still didn't quite understand you, you are talking about cloning here... I'm gonna have to get a bit technical then.
BTW what is wrong with making a full image hdd backup(all of your 6 partitions) and storing it onto your external drive ? That way you will only have one image file to store. When you restore it back to your 250gb drive it will obviously restore all 6 partitions(and the MBR of course).
Don't understand why you want to clone your 250GB HDD onto your 640GB one, yes of course it will delete the whole disk(and it always will) since it is a CLONE you are trying to make. Let me explain it to you... When you make a clone of your HDD it literally makes a clone of everything, what that means is that all the data from the hdd is copied into the clone INCLUDING the partition table layout. Do you see where i am going ? When you copy that clone to another HDD it will also re-arrange the partition table on that drive to be exactly the same as on the original source drive so that means it will destroy the previous partition table layout. It's perfectly logical. That is why it is reffered to as a clone. It is an exact copy.
Also Acronis Disk Director has a disc cloning option, of course it has it. When did it not have it ?