While Windows 8.1 Update 1 won’t be available to the public until April, a few users are claiming that they are getting access to the final Release to Manufacturing (RTM) version of the update (Windows Feature Pack) today by simply adding a Windows Registry key that point to the right Microsoft servers.
The update is a massive 752MB install and it seems that not only you can install the RTM spring update on Windows 8.1, but you can also install the bits on Windows RT devices or Surface tablet.
For those brave users here are the steps you need to follow to install Windows 8.1 Update 1 RTM:
1. Go to the Start screen and type regedit and from the results, right-click Regedit.exe, and choose Run as Administrator.
2. Navigate the following path:
3. Inside the Microsoft folder, right-click Windows and select Key. Now name the new key: SHWindowsPoolS14.
4. Restart your computer and then launch Windows Update and check for new updates. Now you should be able to see the update.
The first update you should see is: “Update for Windows 8.1 for x64-based Systems (KB2919442) – (S14 Prerequisite v01.0008)“. This if the first update, go ahead and install. Follow the install restart your PC, check for updates again and now you should see the actual bits (KB2919355).
Keep in mind that this is the pre-release version of the Windows Feature Pack update and it is intended for PC makers and selected testers. We don’t recommend the installation until the actual public release and be warned that modifying the Windows Registry can cause the system to be unstable.
Update: It seems that the workaround has been already blocked by Microsoft, as many users aren’t seeing Windows 8.1 Update 1 anymore after following the process described above. However, you can also find the download links for the files at MDL Forums here, but I recommend waiting for Microsoft to officially release the update.
Source MDL Forums