Why does factory reset not complete?

I have recently reset my device to its factory settings as it was becoming slow and now holding power as well as it had done previously. This was successful but as I have been going through the set up process this has become stuck on the "This tablet belongs to" page. I have entered a name several times and clicked 'go' and the bar appears to be processing. However despite being left for several hours it is still on the same page. I have tried rebooting several times and still the same problem. The tablet is now unusable! Help!