Extension of the C drive on Windows 7

​The HDD of my Dell Inspiron is divided into C, D and E drives. My C drive is almost full now.​

​I would like to extend my C drive into some space from D drive. I was able to shrink D Drive and there is unallocated space. I tried extending C drive into it but the unallocated space was not on its right. So, it could not be extended into it.​

​How to solve this problem?​