Is there any way to avoid uninstalling of Sun JVM? 

I am using Microsoft JVM for the purpose of certain application. There is no way to avoid it. Because ,the application requires MS JVM and it does not work with Sun's version of JVM.This is how I am locked in Windows XP.I have to uninstall Sun JVM to use that application.  Is there any way to avoid the uninstalling of Sun JVM, still able to use that application? 

It used to be possible to have both the MS and the Sun JVM installed on a single machine, and use both of them.  Why do you think it isn't?  As Campbell said, you need to set the PATH (and possibly the CLASSPATH) accordingly, of course.