I have a Gateway desktop PC and a Lenovo ThinkPad Twist. Both have Windows 8.1. When I try to do the Windows 8.1 update, BOTH fail with error 80070003. I have tried repeatedly using various MSConfig settings, disabling anti-malware software, clearing the DataStore and Downloads folders and installing the update manually resulting in the same error message on both machines. I have a trouble ticket with Microsoft Support which was filed 4/9/2014. The technician spent 6 hours on 4/10/2014 trying to fix the problem remotely on the Lenovo but failed to fix the problem and had to escalate it again. He will resume trying to fix it on Monday, 4/14/2014.