Oh, I wish you had not bought Norton! There are several GREAT anti-virus programs that are free and don't take too much space on your computer. If you notice it getting slow, it will probably be because of Norton.
Usually with updates, such as Java, old versions will be uninstalled, and the newest one will replace it.
Windows updates need to stay put. Never delete any from add/remove programs. Microsoft puts out many security updates that don't take the place of the ones that came before.
If you ever update other programs, such as Word or WordPerfect, and you notice that a previous version remained, you should be okay to uninstall. Don't go in and just start deleting program files though. Just go through the add/remove programs feature.
Something else you should probably do is run a registry cleaner. Go to this
website for a program I use at work. It is free and easy to use. Delete cookies and fix the registry. It's wonderful!
Please feel free to PM me if you have any questions! I'm a computer tech IRL.