I'm guessing you still have the JRE version in your path, even if you also have the SDK. I'm always wrestling with the automatic JRE updater changing my path to point to the JRE version. :-p
I'd look at your PATH and JAVA_HOME environment variables. If they refer to a JRE directory, change that to the JDK directory. Then start a new shell and see if "java -version" has changed.
In the meantime, if you manually invoke the full path to your JDK's java.exe with the -version option, you can see if that one's even a server VM to begin with. :-p If it isn't, maybe try "C:\...\java.exe -server -version" to be sure.