just downloaded 6u10-b32 (have 6u10-b25 installed already) and started the installer.
It says "This software already is installed on your computer. Do you like to install
again?" if press "YES". Then it says "This action is only valid for products which
are currently installed."

So it seems there either was a registration problem with b25, or there is a
recognition problem in b32!

Then removed 1.6.0_10 from machine and cleaned the registry.
also removed 1.6.0_07 SDK. Then installed 1.6.0_07 SDK -- worked well!
Then downloaded the brand new 1.6.0_10 SDK and it shows the Error 25099 error message.

Had tried several times, with and without administrator rights, with and without
reboots between installations -- no chance, always the same message.

It seems to related to GlassFish which can be installed as a Windows Service,
resulting in the JVM beeing a locked file directly after reboot.

JRE should needs a solution that is independent of GlassFish or any other Java products.