J2SE Runtime Environment 5.0 is supported on Windows platforms running on 64-bit AMD processors:
http://java.sun.com/j2se/1.5.0/jre/install-windows-64.html

J2SE 1.6 update 1 is available for windows XP x64 -- but no browser java plug-in included (maybe in future)

So installed both 32-bit J2SE and 64-bit J2SE

32-bit apps like firefox, limewire will use only 32-bit J2SE ... if 64-bit versions come out i will upgrade to them so they can utilize the 64-bit J2SE (if by then it includes the java plug-in)

cheers