Windows XP don´t have Java pre-installed, cos Microsoft prefferred working with Adobe(macromedia) Flash, due a misunderstanding of the two parts: Microsoft and Sun. You can download Java at
http://www.sun.com/java .
For Windows 98, it haves a very old Java version (1.x I think). So, it can be uncompatible with nachazo´s addon.
For nachazo: Che Gue Vara rox, but Pele is better than Maradonna. Sorry, I needed to tell you it :( sorry a lot