As far as I can tell, in a few months there'll be no more support from Microsoft for Windows XP. I don't know if they'll even leave Windows Update running. Until they turn it off though, here is a quick bit of advice on how to go from a fresh install of Windows XP Home (specifically service pack 3, though it may be all versions) to a fully updated one.

There is a problem if you don't do this as described below. Essentially the computer will almost freeze when running Windows Update. The CPU shoots up to 100% on a process called SVCHOST.EXE. This hogs all resources and Windows Update fails. The root cause is something like this.

There is some weird interaction between the latest security updates, the "automatically install updates" option, and Windows XP.

It's made worse if you have the automatic check for updates on, but it doesn't go away if you turn it off. The system hogs resources.

There's an easy fix. If your Windows Update fails and task manager shows SVCHOST.EXE taking 100% CPU for ever, then you need this fix.

If you are installing from fresh and try to do this fix too early, then you also bugger up the system.

Quick description of the fix - install Internet Explorer 8 and its cumulative security update.

Simple.

Here are the steps from a clean XP installation.

1. Keep automatic updates off.
2. Run Windows Update - this will install some ActiveX or whatnot and take you to a page offering you Microsoft Update instead.
3. Choose to run Microsoft Update - this will install another ActiveX and then check you have a genuine Windows installation. It will eventually take you to the Express/Custom updates page. Stop there.
4. Install IE 8 from Microsoft - https://www.microsoft.com/en-gb/download/internet-explorer-8-details.aspx
5. Install the cumulative security patch for IE 8 - http://technet.microsoft.com/en-gb/security/bulletin/ms13-097 - scroll to Windows XP/IE 8
6. Then go back to Windows update and use it as normal
7. When you're happy it all works, turn on the automatic updating