title: Change environment variable (JAVA_HOME) without logging out
body: <p>I'm currently developing in 3 different Java versions and therefore often change my <code>JAVA_HOME</code> variable. However, I have to log out in order to get the variable updated. I update it via <code>System Properties -&gt; Advanced -&gt; Environment Variables</code> (Windows XP).</p>
  
  <p>Surely there is a smarter/easier way of doing this.</p>
  
  <p>I guess I could use the SET command in prompt, but that is not permanent and as I often use one Java version for a period of time I don't want to reset it every time I start the PC.</p>
  
  <p>Any suggestions?</p>