It’s amazing the moving parts in Oracle Database 11g, and the ones that I don’t use after installation for a while often reach out to teach me something new. That’s what happened when I went to launch SQL Developer on my Windows 7 Professional 64-bit installation.
I got the message Unable to find a Java Virtual Machine, as shown in the image below. It really means unable to find a 32-bit Java 5 or Java 6 (1.6.0_4+) SDK home. Although the installation appeared fine, it pointed the SQL Developer configuration file to an incompatible 64-bit Java 7 SDK.