Microsoft will drop support for Windows XP on April 8, 2014.
While there are sources that state the Microsoft downloads will still be online afterwards for people to update their machines, there are no guarantees of this. Microsoft is only obligated to host these files until the end of support. Windows Update for Windows 95/98 and NT were pulled offline a few years ago and no longer functions.
You'll simply need to click the following link, which will give you the option to pick a date from which you'd like to download the service pack.
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