Windows 8: Upgrading to Windows 8.1
Microsoft Windows 8.1 is a free upgrade to Microsoft Windows 8, somewhat analagous to a Service Pack. Relatively soon, Microsoft will stop issuing updates for Windows 8 so Windows 8.1 is an important update. As of early 2014, machines in the supply-chain still contain Windows 8 so the best time to upgrade is before the machine goes into production.
The Windows 8.1 Update will appear in the Store if the machine is ready to be upgraded. If it doesn't appear, in most cases this means that the updates KB2871389 and KB2917499 have not been installed. This can be done via Windows Update. (It is not necessary to apply the other updates, to save time and bandwidth.)
After rebooting, the upgrade should appear in the Store. If you select it, it will download, install and reboot automatically.
Some applications which need to be uninstalled before the upgrade will continue are:
When the upgrade is completed, if the machine is not domain-joined, Windows 8.1 will prompt to sign in with a Microsoft account or to create a new one. This is not necessary, and you can continue to use the local accounts that were on the system. To do this:
See Windows 8/10: Recovering Disk Space After Upgrade.