You will need to:
- Free up space to the immediate right of the C drive, in what I am presuming is your D drive.
You can either:
a) move all the data from D to another partition or disk, or
b) if there is more tha 50% free in D you can shrink it, create a new partition in the newly created space, and move the data from D to the new partition. (thereby moving all the data rightwards)
- Delete the now empty D drive.
- Extend the C drive as far as you wish into the newly created space.
- Tidy up by following similar steps to create space and amalgamate into the drive structure you want.
One thing I have been told is that sometimes the Disk Management has difficulty with extending into space of a different partition type eg primary, secondary or logical. In this circumstance a quick look at some freeware disk management software would be wise, eg Minitool Partition Wizard Home or EaseUSPartition Master Home.
Don't pay for them! The freeware versions are all just as good for basic use.