Here is a similar thread: Re: Installing sql developer
Just point to a JDK rather than a JRE. Make sure the SQL Developer and JDK downloads are either both 32-bit or both 64-bit. Avoid jdk1.7.0_xx for the time-being. And you can always download the 32-bit SQL Developer that comes with a jdk (it has jre in the name, unfortunately).
SQL Developer Team