Q:

How do I correctly install the Facebook SDK Unity plugin? 

My current process is approximatly:
I start with a Disk image of Window 7 x64 with only:
Unity 4.3.3f1, Located 'C:\Program Files(x86)\Unity'. 
The adt-bundle-windows-x86-20131030. ' C:\Users\Will\adt...'. 
The Java 32bit runtime 1.7.0_51-b13, 'C:\Program Files(x86)\Java'. 
'C:\Program Files(x86)\Java\jr7\bin;' is manually added to my 'Path' Environment Varible. 

As it is I can cleanly deploy Android projects, however I want to use the official Facebook SDK plugin.  At this point on my first attempt to install the plugin I dropped it into a project as per the official 'Getting Started' tutorial and this is where I get a bit lost.  Even though there is no mention of it in the 'Getting Started' tutorial I find that OpenSSL is a dependancy of the SDK. 
So I install the OpenSSL binary 'Win32OpenSSL-1_0_1f' to 'C:\Program Files(x86)\OpenSSL-Win32' and when the plugin still can't find it I add 'C:\Program Files(x86)\OpenSSL-Win32\bin;' to my 'Path' Environment Variable. 
At this point The plugin's 'Debug Key Hash' starts working and I naievly assume that everything is correct, However; When I attempt to deploy a build I recieve the following error:
Error building Player: Win32Exception: ApplicationName='C:\Program Files (x86)\Java\jre7\bin\javac.exe', CommandLine='-bootclasspath "C:/Users/Will/adt-bundle-windows-x86-20131030/adt-bundle-windows-x86-20131030/sdk/platforms/android-19\android.jar" -d "C:\Users\Will\Documents\Unity Projects\test\Temp\StagingArea\bin\classes" -source 1.6 -target 1.6 -encoding ascii "com\DefaultCompany\test\R.java" "com\facebook\android\R.java"', CurrentDirectory='C:\Users\Will\Documents\Unity Projects\test\Temp\StagingArea\gen'

and the build process is halted. 
Could anyone help explain where I am going wrong and to get this plugin to behave? 

A:

I had the exact same issue - I've solved it by deleting the JAVA_HOME environment variable that pointed to a directory containing JRE (instead of JDK).  You also seem to only have JRE installed and the javac.exe file is not part of that package.  Alternatively, point JAVA_HOME to the directory on your machine that does have JDK (and javac.exe) installed.