If you find that your upgrade download is still hovering around the 0% mark then Tweakguides has this great piece of advice:
Update: Keep in mind that Windows 8 is steadily being released around the world in different time zones, so it may not be available for your region just yet. If the $39.99 upgrade purchase link above doesn't work for you, you can either use this Microsoft Store link and select Windows on the main page, or download and run the Windows 8 Upgrade Assistant to initiate the upgrade purchase.
