Hi ShY
Now! Go to,
START/Set Program Access/Change or Remove Programs,
now completely remove all versions of java.
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
Disconnect from internet, close ALL apps n reinstall java.
Follow thease instructions exactly.
Vista needs java JRE 6
Shout if you need help.
Peace.