The Java installer is worse than annoying, it's unreliable and capable of screwing itself beyond recovery.
The well known 'Error 1723' which Sun/Oracle have still not worked out a reliable fix for, continues to plague people. The one attempt at a fix that they produced, was pulled after it didn't work and actually made the situation worse for many people. Now you are on your own.
I recently encountered this after the Java update failed to complete correctly.
It took me half a day carefully sifting through the registry and killing off all references to Java, before I got it to a point where I could re-install Java and get it working again.
If it wasn't for a particularly stupid java app that I require, I'd never let this junk loose on my computers.