Question: After choosing between "Express" or "Custom" update it keeps loading forever.

![windows update screen](https://i.stack.imgur.com/MkvQ8.jpg)

![windows update keepes loading forever](https://i.stack.imgur.com/CpMj8.jpg)

That's how it looks like.

I have been waiting for more than 24 hours, but no success.

**SYSTEM & ADDITIONAL INFO**

* Three computers were reformatted and are presenting the same problem.
* Same CD have been used on all installations.
* No problem occurred during instalation.
* There is no problem with the network
* Windows Version: XP SP3

Answer: 
I did have exactly the same problem as stated by RaphaelVidal.
In my case the solution was actually simple.

Cause of the problem looks to be a cancelled download or install of an earlier update. I could see that in the update history (see left side in Microsoft Update) that an earlier update was cancelled.

In that history a "KB-number" of that cancelled update is shown.

The solution is to Google on that " + download + Microsoft". And than download and install that update manually.

After that install, in my case Microsoft Update was working again.

(Maybe you see more cancelled updates in the history and you should repeat the above).
If anyone gets here from the future (well, the past is a bit unlikely), and can't get Microsoft Update to work, with it constantly Checking for Updates but never finishing, along with svchost.exe high CPU usage:

Try disabling Microsoft Update, at the bottom of the Settings page, linked to on the left in Windows Update site. For some reason, if enabled, checking for updates never finished.

I tried manually updating root certificates, IE8, etc, and a bunch of hotfixes, but they did not work. Disabling Microsoft Update cleaned everything right up.

Hope it helps someone.