It's always possible to have corruption in downloaded files but as we're moving away from Dial-Up Internet connections don't see it very often. The 8.1 Update is strictly a download from the Store for most users and automatically installs it would be presumed to be correct if Windows 8.1 Update completes then runs seemingly properly. I just did one, started the download on a Gateway before bed and all was good this morning. The Update wipes out the list of installed updates in Control Panel, Windows Update that were installed in 8.0 and I only had 6 updates to do today. I did have to do the 8.0 updates yesterday before 8.1 would start.