From Fred Langa’s column in Information Week:
But not swiftly: The update process can take a considerable chunk of your workday, even if you don’t count the download time or install from the free SP2 CD. Twenty to 40 minutes seems about the norm for installs on faster PCs; older, slower systems can take well over an hour.
There’s not a lot that can be done about that, but you can achieve a huge time savings on future installations and reinstallations of XP by integrating SP2’s files with those of your original XP setup CD. Your hybrid install CD will work exactly as the original one did, even to the point of using the same 25-character Product Key, but it will be completely up to date with all patches and updates, up to and including SP2. Any system you set up with the hybrid CD will be pre-patched to current levels, in one step. You’ll be totally up to date from the start, rather than facing maybe an hour or more of additional downloads to bring the new installation or reinstallation to SP2 levels.