Its now available from Microsoft:

http://download.microsoft.com/downlo...35-SP2-ENU.exe
(UK and US English Installs Only - Others soon to Follow)

Or you could wait till the 25th of Augest and get it Automatically off Windows Update.

and in regard to EvilMonkeys comment, I would recommend installing it stright away, it offers improved protecton for Internet Explorer (making it the most secure Browser out atm) and a number of important security updates to Windows XP. If you dont install it now, you will be forced to eventually

And as you can see from the reason of this thread, JJ2 will work with SP2