Partition magic is what you need, its not free but its a wonderful bit of software.
one bit of advice though, when you come to resize your partition, lock your pc away in a room once you start and go out for the day, as this program can take A LONG LONG time to finish resizine, and its all too tempting to think its failed after a few hours and junk yor hard drive by rebooting, saying that 16gb to 74 gb shouldnt take more than a few hours
your other option is to forget about a resize and just create an NTFS partition in the free space, you can always install the majority of program files there is your running out of room, even transfer your my documents folder to it if you need to.