New to Java

I'm new to Java and I'm preparing to teach myself Java at home on my own and with any help I might find.

I was looking at the progams installed on my computer (from Dell using Windows XP) and found a number of Java programs installed. some of them look like new versions of older Java programs. I was wondering if I should remove any of them or if they will conflict with each other?

Here is what I found listed on control panel software:

J2SE runtime Environment 5.0 Update 10
J2SE runtime Environment 5.0 Update 11
J2SE runtime Environment 5.0 Update 7
J2SE runtime Environment 5.0 Update 9

Java 2 Runtime Environment, SE V1.4.2_03

Java(TM)6 update 2
Java(TM)6 update 3

Java (TM)SE runtime environment 6 Update 1

Are all these programs necessary? Can some of them be removed? is there any harm in removing them or leaving them?

Any help would be appreciated.

Bill