It looks like you are using mint4win. If so, you do not have a true dual boot. You are running Mint inside of Windows as a program. If this is the case, as far as I know your only option of removing Windows and running Mint alone is to run your live Mint DVD and do a complete fresh install of Katya, selecting the option to use the entire hard disk for the installation. Sorry, but it would mean having to reinstall whatever applications you may have installed since your initial installation. Just be sure to back up any personal data (music, photos, videos, etc.) to an external source first, such as a DVD+RW or USB stick.
HP Pavilion 17 Notebook, 8GB DDR3, 2.5GHZ A10-APU, Radeon HD 8650G
Registered Linux User #520972