While building a SharePoint 2013 environment, I came across this error when running SharePoint 2013 installation.

A system restart from a previous installation or update is pending

The pre-requisites wizard had successfully installed the required dependencies and restarted several times. And so did I manually restarted the server but in vain.  Looks like this was due to a registry entry that did not clear the session state from pending restart to clear. So, change the following registry key and re run the installation. Lo and behold, the installation started. But make sure you have restarted the server before you make these changes to ensure any genuine pending request for restart are cleared.

Open the Registry editor (run > regedit)
•Navigate to this path “HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager“
•Rename the “PendingFileRenameOperations” value to “OldPendingFileRenameOperations“
•Reboot the server

Now proceed with a clean install.