FULL PRODUCT VERSION :
java version "1.6.0_01"
Java(TM) SE Runtim Environment (build 1.6.0_01-b06)
Java HotSpot(TM) Client VM (build 1.6.0_01-b06, mixed mode, sharing)

and
 
java version "1.5.0_11"
Java(TM) SE Runtim Environment (build 1.5.0_11-b03)
Java HotSpot(TM) Client VM (build 1.5.0_11-b03, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows XP [Version 5.1.2600]

A DESCRIPTION OF THE PROBLEM :
When I have concurrent installations of 1.5.0_11 and 1.6.0u1, when I remove 1.6.0u1, the system does not recognize that I have 1.5.0_11 installed to use the associated webstart. An attempt by the system is made to reinstall webstart (1.5 in this case). This is done by installing the latest jre (1.5.0_11) which is already installed. The install fails and a selected application does not run.

This seems very similar to bug id: 6252614 only for different versions.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
demo_page = http://java.sun.com/products/javawebstart/demos.html
load_webstart_page = http://java.sun.com/products/javawebstart/needdownload.html?

Steps:

1. No version of Java installed on the computer and just rebooted.
2. Open IE and navigate to %demo_page%
3. Try running the "Application Manager" demo at the bottom of the page.

Results: You are redirected to %load_webstart_page%

4. Close IE
5. Install jre 1.5.0_11
6. Open IE and navigate to %demo_page%
7. Try running the "Application Manager" demo at the bottom of the page.

Results: The "Application Manager" application starts and runs.

8. Close IE
9. Install jre 1.6.0u1
10. Open IE and navigate to %demo_page%
11. Try running the "Application Manager" demo at the bottom of the page.

Results: The "Application Manager" application starts and runs.

12. Close IE
13. Uninstall/Remove jre 1.6.0u1
14. You can reboot now if you want, but it didn't make any difference for me.
15. Open IE and navigate to %demo_page%
16. Try running the "Application Manager" demo at the bottom of the page.

Results: You are redirected to %load_webstart_page% (No webstart installed..)



EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
I would expect that once I uninstall jre 1.6.0u1, the system would recognize that I have 1.5.0_11 installed and use this webstart appropriately.
ACTUAL -
The system behaves as if I do not have any webstart installed and tries to install the latest member of the "family". The install fails because I already have the latest family memeber installed.

ERROR MESSAGES/STACK TRACES THAT OCCUR :
In a dialog with the title "J2SE Runtim Environment 5.0 Update 11 Instal..." I get a warning message:

" You already have this version of the JRE installed. Please uninstall the product trhough your add/remove programs utility before reinstalling."

and an OK button.

Or, in the test scenario listed above, you get redirected to a page to install webstart.

REPRODUCIBILITY :
This bug can be reproduced always.

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See Steps to reproduce...
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CUSTOMER SUBMITTED WORKAROUND :
jre 1.5.0_11 must be uninstalled and then reinstalled.