Temp. Internet Files Cache Size

Under the temporary internet file settings, the amount of disk space to use is set to 0. When I attempt to change this, I get a dialog box saying “Please select a value between 1 and 0 for how much disk space temporary internet files may use.” It will not accept any value at all here. As you might guess, this really slows down internet access times when revisiting pages. Is this controlled in the registry someplace? Any help would be MUCH appreciated.