Since support is going away next year, how could I
backup my security fixes so that I can restore them
in case my O.S. has to be rebuilt.
On installation, each WinXP security update generates
a new folder in c:/windows with the filename
$NTUninstallKB and a string of numbers. Each also
includes an EXE file and INF file and a TXT file that informs
you what it does. You can copy all these $NTUninstallKB
files on a CD like your SP3. (I do not bother because I
clone c:/Windows and c:/Documents and Settings
from time to time.)