When I launch SQL Developer 4.0.2.x, I get the above message.
I have installed jdk1.7.0_55 in C:\Program Files\Java\jdk1.7.0_55
So, as instructed in that window, I edited the sqldeveloper.conf file and set :
SetJavaHome C:\Program Files\Java\jdk1.7.0_55
When I launch sqldeveloper.exe, I get the same message (above) again.
What am I missing?
Nothing - that error message has a bug in it - it's directing you to the wrong file.
Go to your Windows User AppData\Roaming\sqldeveloper\126.96.36.199\product.conf file and set it there.