OS - Win2000 Prof, Win XP Prof - fcs
Hardware - Intel
Browser - NS6.1
JDK Build: 81

Steps to Reproduce :-

-Make sure the system has Netscape 6.1 installed

1. install JDK13.x on Windows machine , This is important since this bug can be produced only on a system where JDK1.3.x is pre-installed before installing 1.4.0-beta3 . I installed jdk1.3.0_03 and jdk1.3.1_01ea-fcs first

2.Install any of these JDK/JRE
j2re1.4.0-beta3-i.exe
jre1.4.0-beta3.exe
j2sdk1.4.0-beta3.exe

3. Verify from Netscape About plugin that plug-in is upgraded from 131 to 140

4.Uninstall the Java Runtime Environment of 1.4.0-beta3

5.When the uninstall is reaching completion , User will be prompted with the Modal Dialog Box saying:-

Cannot install java plugin for Netscape Navigator from <d:\progra~1\...... >
it may be caused by following reasons ......
See Error message here http://javasoft4.india/Java_Install/bugs/images/error_uninstalling_j2re140_b81.gif
This can be related to Bug 4496392 & 4492927

i was able to reprouduce this bug on two Win2K and two WinXP machines

My guess is JDK1.3.x plugin for NS6.1 conflicts with 1.4.0-beta3 plugin since when the installer is trying to remove NPJava32.dll file this error message pops-up