How to Resize the C partition in Windows 7

It's quite easy but to tell you its possible to decrease the volume size of a drive but not increase it without losing data.  To decrease your C drive volume size, follow these steps:

Right Click on my computer >Manage > Select Disk Management(under storage on left hand side) > Right Click on C drive > Click shrink volume. Shrink the volume as much you want. 

However, Windows 7 Disk Management allows you resize partition, whereas its limitations will let you down and can not resize partitions to be desired. Third party tool is available and helpful, for your question, I recommend you Aomei Partition Assistant, which was given several editions to solve various partition problems on different operating systems. Based on your own situation, free partition manager or pro partition manager both helpful for you to resize and move partition.