Yes, you can run two instances of a JVM on one machine. An obvious example would be running any Java based Client/Server application on a single machine. If you want to learn more about the JVM, then you could try the Java Virtual Machine Specification. You can find it here at the Java Ranch in the Bunk House.
Dan Chisholm<br />SCJP 1.4<br /> <br /><a href="http://www.danchisholm.net/" target="_blank" rel="nofollow">Try my mock exam.</a>