windows xp - Can't upgrade to JRE 1.6 from 1.4.2

For the life of me I can't get my JRE upgraded. I've ran JDK6u21 and nothing, re-installed and nothing, tried JRE6u21 and still

java version "1.4.2_06"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.2_06-b03)
Java HotSpot(TM) Client VM (build 1.4.2_06-b03, mixed mode)

Any suggestions? Can I force to 1.6? The 1.6 directory is in my path, don't even know where 1.4 is.

Answer

If you aren't using JRE 1.4.2, uninstall it. You didn't mention which operating system you are using, so there may be some catch related to the OS which needs special attention.
For example in new versions of Ubuntu you have to run

 sudo update-alternatives --config java

to configure java.

If 1.6.21 is in your path, and java -version in terminal reports what you wrote, check your path. 1.4.2 is in it before 1.6.21. The obvious solution is to remove old version from path or to place new before old.