Good, that's what I thought.
In that case you have two choices...
1) Create a second partition in the unallocated space. To do this, right click on the second block (the one marked unallocated), select 'Create partition' & follow the instructions. You'll need to create a 'logical' partition & format it using NTFS. Afterwards, when you open My Computer, you will see 2 hard drives instead of one. You can use the new drive for anything you like, eg downloading files to, backing up data to or just as a general storage area.
2) Use a third party utility to extend the size of your C drive so that it becomes 232GB in size.
Personally, I recommend you go with option (1). This doesn't require any third party utilities & is safer because it doesn't affect the C drive. It's also really useful to have at least one other partition (drive) apart from the C drive because it allows you organise your file storage better.