Trying to either install Diablo 3 or update it and you are getting an error “appears to be corrupt” that is preventing the game from installing or updating? This issue is usually caused by a speed decrease in the download speed of the file (usually occurred by either Blizzards servers or your own internet connection)_ try the following below to fix it.
First thing, delete the corrupted update file and resume your Diablo install/update (C:Program Files (x86)Diablo IIIUpdates)
Another option is to install the game in a separate folder or if possible hard drive , so instead of installing it in C:Program Files (x86) install it to C:Diablo III
If you still get the same issue it has been reported that removing the update file and trying again till you get a better server connection has worked but not guaranteed._