I have just installed windows 7 pro 64 bit, a new installation. Next came Java 1.8.0_171 followed by a new download of B4J 6.30. Lastly Dot.Net 4.52 installed as B4J wouldn't start. Rebooted.
I started B4J and wanted to set the paths. The browse button to set Javac.exe does nothing! I had to type it in: