I just installed Windows 8.1 update to my business computer. Here are the troubles I ran into when doing the install.
First, you need to find the update - it's in the Windows App Store and has a big tile that you can't miss. Notice you cannot find this update unless you have done the latest Windows Update to get the latest patch to the Windows App Store. You will not see the Windows 8.1 update in your Windows Update session - you can only get it from the Windows App Store.
Be sure that you have backed up your system before installing this OS update in case something goes terribly wrong.
Before installing this update - to eliminate any problems during the installation, uninstall any third-party anti-virus / firewall programs you are using. Reboot your computer, then start the download and installation of Windows 8.1 update.
Once the computer finishes the update (after several reboots), follow the on screen instructions to complete the update. Reboot your computer and then re-install your third-party anti-virus / firewall programs for a flawless installation.
Now you can enjoy the latest Windows OS version - this one looks and acts friendlier than Windows 8.