It is recommended that you connect to an un-metered connection or public Wi-Fi connection and then check for and install the Windows 8.1 Update.
Also ensure that the Servicing Stack KB2919442 is installed on your computer, as it is a prerequisite for Windows 8.1 Update.
It should therefore first be installed on your system before your attempt to install Windows 8.1 Update or KB2919355. 1] If your Windows 8.1 Update has failed to installed, you need to clean up the corrupted installation.
Open command prompt as administrator, type the following and hit Enter: You will get a list of packages.
Since KB2919355 has not been successfully installed on your computer, you wont see it, but you can see it installed on my 64-bit system.
This operation takes 15 minutes or more depending on the level of corruption.
More on this at post titled Windows Component Store Corrupt. But if think that your Windows Update client is already broken, use a running Windows installation as the repair source, or use a Windows side-by-side folder from a network share or the Windows DVD, as the source of the files.
Additional information about Error Code 0x80070020 is as follows: Windows 8.1 Update is shown as Important, when you open Windows Update, yet it is unchecked by default. Moreover, if you are on a metered network, Windows 8.1 Update will not install automatically even if you have Automatic Update turned on.
You will have to to connect to an un-metered connection or public Wi-Fi connection to install the update.
To do this, run the following command instead: with the location of your repair source.
2] KB2939087 recommends in case you are unable to install the Windows 8.1 Update package KB2919355 via Windows Update, then you should download and install the package manually. 6] If you receive Error 0x80071a91 when installing update KB2919355 in Windows see KB2956283.
If you are facing these problems, check out following tutorial: If you are unable to download Windows 8.1 from Windows 8 Store and it gives you error message that the update is not applicable to your computer or country, you can try the steps given in following tutorial: When you try to install Windows 8.1 using Windows 8 product key, you receive invalid or incorrect product key error message even if your product key is genuine.
If you also face this problem, check out following tutorial: This problem is faced by Indian users mainly.
It includes usability improvements, extended mobile device management and improved hardware support.