So, is the rest (which is fat32) assigned as a different drive, such as D:? If so, you can delete that partition and then resize the C: drive using the unused space from D:.
To do this, you need to go into the Disk Management Utility. In the search bar in your Start Menu, type in "create and format" and then click the link that shows up for the Disk Mgt. Utility.
Next, you'll see a list of all the drives you have on your machine. Right click on the FAT32 drive and select "Delete Volume".
Next, right click on the C: drive where you installed Windows 7 and click on the "Extend Volume" and you'll be able to add the space that was the Fat32 drive.
What I would suggest is possible extending the C: drive to another 100 gigs and then create a D: drive partition as NTFS with the rest.
In my case, I have 3 drives in my system, so I use all the space on the first HD for my C: drive. The 2nd drive I use all the space for my D: drive and the third drive (which stores my TV recordings) is used as the E: drive.