OS : Windows
JDK/JRE : JDK 1.3x / JDK 1.1x

Steps To Reproduce:

1.) Install J2SDK 1.4.0 (FCS)
2.) Install J2SDK 1.3.0 over existing J2SDK 1.4.0 (FCS)

Results :

During the JDK 1.3.x installation process though it displays saying "Setting up Java 2 Runtime Environment " It will abort the public jre installation and no error messages will appear, resulting with no 1.3 Runtime on the system.

Due to this problem the user cannot use JRE 1.3 bundled in JDK1.3 when installed over JDK1.4 and he would be forced to use JRE1.4 .

Here is how the reg keys are pointed when J2SDK1_3_0 is installed over J2SDK1.4.0-FCS

Reg Keys(JDK Current Version) : 1.3
Reg Keys(JRE Current Version) : 1.4
When you do java -version on command prompt shows "1.4"