Merging 2 partitions (System+Data)

In my 500 GB HDD, I have 4 partitions (C,D,E,F). I purchased my desktop a month ago & unfortunately, the stupid computer guy made just a 50 GB partition for the system drive (C, Windows 7 Professional 64-bit).

I installed EaseUS Partition Master Free Edition.
This is the screenshot of the present state of my hard disk.
Note:Disk 1 is the Internal HDD. Disk 2 is the External/Portable HDD. Disk 3 & Disk 4 are of Samsung Galaxy Ace which was connected in USB Storage mode at the time of taking the screenshot.

http://www.flickr.com/photos/93984650@N06/9462863961/

I want to merge E: with C:. But when I select "Merge Partition" from C: (by right-click) then E: is grayed out. Instead, D: is not grayed out & it is the drive where I have installed all my games (& not stored setups but 'installed').

How can I merge C: & E:?