Yes it is possible to re size the drives.To resize drive-
1-Open the 'Disk Management'(Search in start menu)
2- Select the drive you want to use to extend C drive and right click on the drive.
3-In the list select 'Shrink Volume'
4-In the dialog box which appears put the necessary information and click on 'Shrink'.
5-Now the space shrinked is un allocated.
6-Right click on C drive and click on 'Extend Volume' and add the necessary information and click on extend.