You still need a finger to drag with. Look in Preferences/Accesibility for trackpad options. I'm using OS X 10.8.2 so the option may be in the same area but different location. With 10.8.2 open Preference/Accessibility then select the Mouse and Trackpad option. You should see a "Trackpad Options" button to click on then check "Enable dragging", I set it to "without Drag Lock". With this enabled you can double tap and hold on the top of windows then drag. Drag Lock requires an additional tap to release.