I would have hoped that Oracle bundled the SQLDev with the Java.Note that the very first download offered is Windows 32-bit - zip file includes the JDK1.6.0_35 (also 32-bit). See here...
downloaded and unzipped sqldeveloper64-3.2.20.09.87-no-jre.zipyou are expected to specify a 64-bit JDK, which gets installed to
C:\Program Files\Java\jdk1.6.0_37\binrather than
C:\Program Files (x86)\Java\jdk1.6.0_37\binThe basic rules: