Microsoft accidentally released the Update 1 for Windows 8.1 this morning. It has since been taken down. However, some folks were able to jump on it and update early. The rest of the public will have to wait until April for the full release. However, those wanting to update to the RTM version of Windows 8.1 Update 1, there are other means to update. Some aren't suggested (torrents, etc.) as they can contain malware within the packages. Some are very legit, but you do take a risk when downloading those.
While the software maker is expected to release the update officially in April, Microsoft has only detailed a few of the features in the update and has not yet provided an official release date. Links to download a final version of the Windows 8.1 Update, thanks to Microsoft’s Windows Update service, have been discovered. A series of patches are required to obtain the full update, but once installed the new desktop-friendly features are enabled.The update can be downloaded via a registry change, or through direct links, but we recommend waiting for Microsoft to officially release it through the normal Windows Update channels in April.