Hi,
You can do a Reset OR a complete re-installation.
How to restore, refresh, or reset your PC (Windows 8 & 8.1)
http://windows.microsoft.com/en-US/windows-8/restore-refresh-reset-pc
Download Windows 8.1 ISO Using your Windows 8.0 Key
http://mcakins.com/2013/10/19/download-windows-8-1-iso-using-you-windows-8-0-key/
Download Windows 8.1 iso
http://philipyip.wordpress.com/download-windows-8-1-iso/
Download the Windows 8.1 ISO using a Windows 8 key and some simple trickery
You can also make a Recovery USB drive.
How to Create a Recovery USB Flash Drive in Windows 8 and 8.1
http://www.eightforums.com/tutorials/5132-recovery-drive-create-usb-flash-drive-windows-8-a.html
On Nov. 15, 2013 Windows 8.1 Back-up Media will be available for purchase. Newegg and
others will be offering the disc,
Windows 8.1 'Back-up Media' disc available to buy soon
http://betanews.com/2013/11/05/windows-8-1-back-up-media-disc-available-to-buy-soon/
Hope this helps.
Rob Brown - Microsoft MVP <- profile - Windows Expert - Consumer : Bicycle <- Mark Twain said it right!