Just bought my mum a Lenovo C340 All-In-One from PC World, and tried to set it up.
All was fine, except that it had trouble installing apps. When I checked, I found that all the Win8 metro apps wanted to update, and the update was failing.
Not only that, but basic Windows Security updates were also failing. When doing the default complete update, as of today, there were 38 updates. When downloading/installing them all, then on the reboot, the update got to 30% complete, then failed. It tried again, and failed again, and rolled back.
I tried using Windows Troubleshooting, which did things like restart the service, but those made no difference.
In the end, I went to Control Panel, and opened Windows Update in the desktop, then manually installed the updates in batches, restarting between each. Although it took around ten restarts, it was successful, and the OS is now fully updated.