Question:
I don't know which version of Java is installed on my computer. How do I figure out which one it is?

Answer:
If you're using Windows, go to "Start->Run". Now type "cmd" (without the quotes) and press Enter. Now type "java -version" (again without the quotes) and you'll see the version information being displayed on the command line.

If you're using Linux, I guess you already know how to open a shell and do the same... ;-)