Linux Mint is spun from an Ubuntu base and probably comes with the tools you need to get your system to dual boot. But, you should prepare your system before you give it a go. First, defrag your C:\ drive and reboot. Then you need to look at how your drive is partitioned now. Ignore what My Computer shows, you, because it won't show you the whole truth. Go to Control Panel -> Admin Tools -> Computer Management -> Disks to view the partitions that are there. There may be hidden recovery or system partitions on your disk that Windows Explorer or My Computer won't show you. If the recovery partitition is at the end and you change it's partition number or delete it, you will no longer be able to use it, so make sure you used your vendor's tool for making a full set of recovery disks, not just the emergegy Windows boot cd. If there is a system tools partition at the end, it contains diagnostic software for checking memory and other hardware for problems. This, too, will be unuseable if you change the partition number.
The Windows disk manager will allow you to shrink (decrease) the size of your Windows partition to free up space for you to install Linux. Most Linux installers also allow you to shrink your Windows partition during installation, too. Those have always worked for me, but you may feel more comfortable using Windows to shrink itself. If you do shrink it under Windows, reboot once into Windows before doing your install. Be careful not to shrink your C:\ so small that you no longer have room to save files or for Windows to create it's pagefile (swap file) or hiberation files or pull its updates.
Regardless of how you shink your C:\ drive, you will still have options. If you created a Windows recovery set, you can delete the recovery partition if you wish, and you can also sacrifice any system tools partition at the end if you want. The installer for Linux Mint will allow you to select to use all available space on the disk, the whole disk, or a custom (advanced) disk scheme. Since you made space, allow it to use all available space. After the install completes, you'll find that at boot you are presented with a bootloader menu that will allow you select to boot into either Linux or Windows.
If before you install you discover that your drive alreay has four primary partitions allocated (e.g 1 small partition, Windows C:\, system recovery, system tools) then your install gets complicated. You'll have to choose to either 1) do a new Windows install (after backing up your data) using your recovery disk set or 2) delete at least one partition at the end of the drive (after your Windows partition) before shrinking your C:\. The second option can get messy, so doing a clean install can be easier since you can select to remove all partitions then create a smaller C:\. The Linux portition of your disk can be left unallocated during a Windows install since the Linux Mint installer will know how to use the left over space to create it's partitions.
Good Luck.