Well look first thing you have to do is press Ctrl + Alt + F6 and you will see a window where you have to put the password you provided it when you installed it and there you will get the option to turn it off, it follows that you have to do is turn it off, hence restart the PC and uninstall.
Now if your problem is that you have the password because the thing is a little more complicated, but has a solution, do not worry, well look here are the steps to uninstall the Deep Freeze without the password, but watch this:
1- restart the PC and enter Safe Mode (You press F8 when you boot the PC).
2 Once inside the failsafe mode you'll start menu and select run, then in the window that you put out and give enter msconfig.
3 From there select the Startup tab and disable the Deep Freeze (you you click on the little picture to the left) appears as the Deep Freeze DepFrz.
4 Then restart the PC and go into normal mode, and you'll have the Deep Freeze off, ready to uninstall without having the password.