Suggestions only :
1. Uninstall your anti-virus program and then try to do the upgrade again. You can always reinstall the AV afterwards. Do you happen to have Avast ?
2. If you are presently running Win 8.1, go to Change PC settings > Update and Recovery > Recovery >Advanced startup > Troubleshoot > Reset your PC, run the Reset. Then try upgrading. Caution, backup four files before Reset.
P.S. I don't have Win 8.1 anymore. So steps mentioned above is by memory. I could have missed a step or 2.