Do you own this phone?
As in, was it running iOS 9.x.x. before you tried to update the OS to 10?
Try disabling firewall and antivirus-software on your computer.
Unplug every other USB-device, and try updating the software of the iPhone again.
If that doesn't help, restart computer as well as iPhone.
One more option would be to use DFU mode to restore it:
DFU Mode for Dummies
Did you also try everything else suggested in this thread?I tried in DFU mode but still error (1).
Did you also try everything else suggested in this thread?