Could not find or load main class org.junit.runner.JUnitCore

You seem to be running under Windows, not LINUX/UNIX. The path separator on Windows is ;, not :. Additionally, you haven't put you jar file in the classpath. So what you want is:

java -cp aJar.jar;junit-4.10.jar org.junit.runner.JUnitCore TestOne

This of course assumes that both jars are in the current directory. You should also always avoid putting classes in the default package.