You cannot simply do a block-for-block clone of a 2GB drive to an 8GB drive - doing so will also clone the partition table and prevent you from accessing the "extra" space.
You need to use a tool that is filesystem aware (like Ghost), or you can extend the partitions on the larger drive. This answer over on Super User covers similar ground (they're talking about going from a big drive to a small one, which requires shrinking partitions. Going to a small drive to a big one requires growing them instead).