I just did it myself buy downloading a free partitioning software and ran the software in windows.
I used EASEUS free Partition Master. You can use this to unallocated you old Linux OS and when you reboot with, lets say Ubuntu live CD, You will be given the option to install along side Windows
Linux makes at least two, usually three partitions when installing so the others you seeing are probably your Mint.
If you decide to go this route be SURE to defragment your windows first and always backup.
You can also use your linux live CD When you install to manipulate you partitions. Detailed info here;
If you Google "dual boot windows and Linux" you will find many tutorials that give you step by step instructions.
Hope this helps a bit.