This is typical for many reasons. From some over reaching antivirus to malware, registry cleaner damage.
Step 2. Backup what you can't lose again.
Now that all is backed up and you know you can copy it back in, use Windows 8.1's refresh this PC feature and if need be reset it to factory condition. That way what's infected or broken will be gone.
My grandfather has not updated his laptop in some time. Trying to install anything gets nowhere, it is stuck on "preparing to install" even when I have selected a single update to install. I am using the updater through the control panel. There are 78 Important updates available and 3 optional ones available. We are trying to update his 8.1 so he can get windows 10. Advice?

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