You can boot the live DVD or USB you used to install Mint, open Gparted and delete the Linux partitions (ext 4 and swap). You will then need to fix the MBR of Windows with your Windows installation disk, or a rescuse CD. Macrium Free works well for this. Be sure to back up your Windows of course before doing this, prefererrably with a system image, which will restore things exactly the way they were before you installed Mint. In fact, that would be another to do it, just make an image and install it on the drive.