I know this thread has existed for a long time, but you may mess up some thing, since from your description, I think you are using windows 7, so the E partition is used for storing booting files. So you have no need to extend this partition. You could use the free space of your C partition to create a new partition for other using.
But there are many people may want to find a way safely and flexibly extend the system partition rather than use build in disk management. And I noted on this thread have not provide the flexible and easy way to resize partition. Before you may know Partition Magic but now it has been out of date, and now there have a alternative software AOMEI Partition Assistant which could manage this flexibly and safely. It is worth to try this software.