To accomplish this, you have to move the D drive to the beginning of the unallocated space, then resize the E drive. Many third-party partition managers are able to perform both tasks.
You could, e.g., download the Ubuntu 12.04 (or GParted) LiveCD, burn it to a DVD or create a bootable USB stick and do the following:
Boot from your Live CD and click Try Ubuntu when it asks whether to try or install it.
Press Win, type gparted and click GParted Partition Editor.
Right-click your D and E drive and select Unmount if it's available.
Right-click your D drive, select Resize/Move, place the mouse cursor over the slider, drag the partition all to the left and confirm.
Now, you have
C: / D: / unallocated space / E:
Right-click your E drive, select Resize/Move, place the mouse cursor over left arrow of the slider, extend the partition all to the left and confirm.
Click the green checkmark labeled Apply All Operations.
Whenever you resize or move a partition, there's a certain risk of data loss (failing HDD, power outage, etc.). Make sure you backup your most important files.