Windows XP SP2 or SP3 archive or downloads?

I use an archive I built from an outdated version of WSUS offline update - in case I need to stand up a windows XP system. You need version 9.21 or older as its the last version that supported XP. Since its downloading the updates directly from MS, and gets the full/offline installers and automatically applies them, these are the official updates and you don't need to rely on windows update for at least the initial update.

This should get your XP box completely up to date, and as of mid december 2016 (when I'm posting it), it seems to update still. This is the best option since it should get your system as patched up as possible, and lets you do so even if XP patches are no longer hosted if you already downloaded them.

It also has lovely logging, and lists of file locations and it lists http://xpsp.dlservice.microsoft.com/download/d/3/0/d30e32d8-418a-469d-b600-f32ce3edf42d/WindowsXP-KB936929-SP3-x86-ENU.exe as the location for windows XP SP3. Of course, this link is likely to die at some point, and I have no XP boxen to test it from. I strongly recommend building your own offline update archive if you think you need it

As of 2017, WSUS offline update v9.21 can't seem to download XP patches. The link for XP3 is still valid.

Do you already have things installed on the OS? If not, it might be faster if you would simply find an ISO for Windows XP that comes with SP3 installed already.

Otherwise, what do you currently have? SP1? Have you installed all regular updates?

I was able to find the Microsoft Update Catalog site which has links for SP3 and SP2.

Once you do get SP3, you should get the Unofficial SP4 to download all updates post-SP3 and receive new updates from Microsoft until April 2019 (I have tested this myself).

EDIT: I should note here, that while this method still works, you will only get updates up until 2019 April 9th, which is when POSReady 2009 (embedded XP) support ends. If you are still using Windows XP past this date, you need to switch away from it, or disconnect from the Internet, to remain secure.

Go to windows update catalogue and type xp (or only KB936929) in search field http://www.catalog.update.microsoft.com/Search.aspx?q=xp
You can find there many others helpful packs.
Good luck