Is it possible to modify a normal servo to a continuous rotation servo? If yes, then how? Can all servos be modified our are there specific ones? Can this servo be modified- http://arduino-direct.com/sunshop/index.php?l=product_detail&p=238.
yes
Yes you can. It has been done many times and I have seen no less than 6 (or more) posts and walk-throughs on this subject.