It is only necessary to set the path to the Maven binary and to the JDK correctly:
set PATH %SystemRoot%\system32;%SystemRoot%;%SystemRoot%\System32\Wbem;%SYSTEMROOT%\System32\WindowsPowerShell\v1.0\;C:\Program Files\Java\jdk1.7.0_04\bin;C:\Program Files\apache-maven-3.0.4\bin
Furthermore you need to set the JAVA_HOME correctly which is done under windows like this:
SET JAVA_HOME=C:\Program Files\Java\jdk1.7.0_04
Be aware of setting JAVA_HOME to the root of the installed JDK and not to bin folder it.
The settings of M2 and M2_HOME is not necessary.