Install the latest Windows 8.1 Update

Windows 8.1 Update and Windows RT 8.1 Update (also known as KB 2919355) include improvements that make your favorite apps and settings easier to find and use, and provide more familiar mouse and keyboard options. For more info, see What's new in Windows 8.1 Update and Windows RT 8.1 Update?

Here’s what you need to know about installing this important update.

It might already be installed

If you’re running Windows 8.1 or Windows RT 8.1 and you get updates automatically, you don’t need to do anything: Windows Update will download and install the update for you within the next few weeks. It won’t interrupt what you’re doing except to tell you that you need to restart your PC to finish the installation.

To check if the update is already installed, go to the Start screen. If you see a Search button near your account name at the top of the Start screen, you already have the update.

After the update, the Search button appears on the Start screen.

The update is gradually rolling out to everyone with a PC running Windows 8.1 or Windows RT 8.1 over a period of several weeks. If you get automatic updates but you don't see the update yet, wait a few days and check again.

Notes

If you're running Windows RT 8.1, this update is automatic. If you're running Windows 8.1 and you want to check your Windows Update settings, see Turn automatic updating on or off.
If your PC is running Windows 8 or Windows RT, open the Windows Store on your PC and update to Windows 8.1 or Windows RT 8.1. This latest update will be included. For more info, see Update to Windows 8.1 from Windows 8.
If you’re not sure which operating system your PC is running, see Which Windows operating system am I running?
If you’re connected to the Internet over a metered connection, you might not get the update until you switch to a non-metered connection and then check manually for updates. For more info, see Metered Internet connections: FAQ.

Install the update manually

If you’re running Windows 8.1 or Windows RT 8.1 and you don’t have the update yet, you can manually check for and install the update by following these steps:

1. Make sure your PC is plugged in and connected to the Internet using a non-metered connection. Don’t disconnect, unplug, or turn off your PC while the update is being installed.
2. Swipe in from the right edge of the screen, tap Settings, and then tap Change PC settings. 
3. (If you're using a mouse, point to the lower-right corner of the screen, move the mouse pointer up, click Settings, and then click Change PC settings.)
4. Tap or click Update and recovery, and then tap or click Windows Update.
5. Tap or click Check now.
6. If updates are found, tap or click View details.
7. In the list of updates, select the update containing KB 2919355, and then tap or click Install.
8. If you're prompted for an administrator password or confirmation, enter the password or provide confirmation.
9. After the installation is complete, restart your PC and sign in.

Note

If you don’t see KB 2919355 in the list of available updates, you might be missing one or more required updates. Follow the previous steps to check for updates, install all important updates, particularly KB 2919442, restart your PC, and then check for KB 2919355 again.

Why you should install this update

We strongly recommend that you install Windows 8.1 Update or Windows RT 8.1 Update (KB 2919355). This is a critical update that is required for future updates to Windows. If you prevent it from installing or you uninstall it, you won’t get some future bug fixes, security updates, and new features. In some cases, if you uninstall this update from a new PC after signing in with a Microsoft account, OneDrive might not work as expected.

Source : windows