Maven 2 and 3 coexisting on Windows

Recentely, I needed to deploy a workspace for a project which is using maven 2, and I'm using Maven 3 for my other projects.
I had to install maven 2, and I had to re set the variables M2 and M2_HOME to make them point to apache-maven-2.2.1\bin and apache-maven.2.2.1 respectively.

I did that, and I got this exception when i ran maven2:

Exception in thread "main" java.lang.NoClassDefFoundError: org/codehaus/classworlds/Launcher

To solve this I had to add to the PATH the following directory: apache-maven-2.2.1\boot.
With this change, maven 2 worked. You can put this environ set commands into a bat file, and run it always you need to use maven 2.