If you purchased your Windows RT before official release of Office 2013 or reset data to factory, you might be using preview version of Office 2013.
Here’s a quick steps to update preview version to release version.
Open control panel, from settings charm.
Open system and security, then Windows Update.
Click view available updates.
Check Microsoft Office Home & Student 2013 RT Preview. Be sure you have enough open space in storage. Click Install and Reboot.
If battery is low, code 8024004C might be shown. Charge your battery and retry in this case.
If windows asks to reboot and nothing happens after reboot, open Windows Update again and start update again.
If update succeed, Office splash will be shown without word Preview.
Office version can be checked at Account tab under File menu.
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