Use http://j2se.sfbay.sun.com/web/bin/view/SQEDeployment/JDKFXPlan#Reinstall_testing (Case 2) as a reference for testing 6u16+SDK1.2.1 cobundle on winXP.

How to reproduce:
You have to clean up the system to reproduce the problem.
1. Run the regular JDK installer, 6u16 (not co-bundled)
2. Finish the install
3. Run the JDK/FX installer bundle from http://jscpreview.sfbay/javase/downloads/widget/jdk_javafx.jsp
4. Verify the "This software has already been installed" dialog for the JDK appears, and click no.

Expected:
5. The FX installer will start

Actual:
Windows Installer thrown (attached) and FX installer is not started.

The problem is not reproducible outside of the cobundle with jdk-6u16-windows-i586.exe from http://java.sun.com