Enlarging an image (or part of an image) WITHOUT keeping proportions

In earlier versions of Photoshop you could take the Rectangular Marquee Tool, place it on an image, create a rectangle, then click on the Move Tool, go back to the rectangle and you could drag a side of the rectangle and just that side would drag where you want it. Now, if you follow those steps, when you drag a side the whole rectangle enlarges proportionately. How do I stop it from enlarging proportionately. I used that function all of the time and I've finally gotten around to asking the community's help. Thanks!