You have several problems, starting with the fact that Windows XP has not been supported since April 2014 and is thus severely out of date and vulnerable to malware attacks. Moreover, Windows XP will only support Internet Explorer up to version 8. IE is now at version 11. Thus, you also have an outdated and vulnerable browser.
Those comments aside, there are many who recommend that Java not be installed at all on your computer, regardless of which operating system or browser you may have. See, for example
Unfortunately, you may need Java for proper operation of a web site that you regularly visit, such as your bank.
Because Java is so frequently attacked and almost as frequently updated, it is good practice to remove old versions of Java. You should have been given the option to remove old versions when you installed Java SE 8 u73.
This is what you should get if you only have the latest version:
If there are old versions, you should get a list of which ones were detected and the option to uninstall them. Do so. If you only have Version 8 Update 73 but still get the notice that “Out of Date Java Versions Were Not Uninstalled,” I suggest that you completely uninstall Java from Control Panel > Add or Remove Programs, reboot, and start over.
As for Firefox, you can check to see what it is using. Open Firefox and type about:addons into the address bar and click on Plugins in the left pane. Scroll down and see what version of the Java plugin is installed:
Opera works similarly to Firefox. See http://help.opera.com/Windows/11.60/en/extensions.html orhttp://www.tomsguide.com/faq/id-2374762/manage-extensions-opera.html