Using gpt.exe leads to exception

When using the gpt.exe on the command line a java.lang.ClassNotFoundException is thrown.
Also when only gpt is typed at the command line the exe file is invoked.
The gpt.bat shall be used to overcome this problem.

Full stack trace:
Error: org.esa.beam.framework.gpf.main.Main
java.lang.ClassNotFoundException: org.esa.beam.framework.gpf.main.Main
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at com.bc.ceres.launcher.Launcher.launch(Launcher.java:148)
at com.bc.ceres.launcher.Launcher.main(Launcher.java:56)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.exe4j.runtime.LauncherEngine.launch(Unknown Source)
at com.exe4j.runtime.WinLauncher.main(Unknown Source)
at com.install4j.runtime.launcher.WinLauncher.main(Unknown Source)