If you are really in a hurry then get your Windows XP Service Pack 3 now:
http://download.windowsupdate.com/msdownload/update/software/svpk/2008/04/windowsxp-kb936929-sp3-x86-enu_c81472f7eeea2eca421e116cd4c03e2300ebfde4.exe
or you could wait a few days...as it weighs in at a hefty 336Mb.