The overlay scrollbars now can be easily switch on/off in Ubuntu 12.10 Quantal using Dconf Editor. This quick tip is going to show you how to do it.
First of all, search for and install Dconf Editor in Ubuntu Software Center
Then open Dconf Editor, navigate to com -> canonical -> desktop -> interface. See, you’ll get 4 scrollbar mode. Set it to normal and you’ll get the fat scrollbar immediately!