First have you turned XP firewall off, if not DO it.
Restart Com.
Now! Go to,
START/Set Program Access/Change or Remove Programs,
now completely remove all versions of java.
Re BOOT Your computer NOW.
Now! Use this Link to get JRE 6, Use the off line installer, NOT the (recormended) one,
http://java.sun.com/javase/downloads/index.jsp
When Download is completed.
Disconnect from internet, close ALL apps n reinstall java.
Do this & get back to us
Peace.