If your installation is stuck at 0% or you are receiving a download failed message, we have found this to usually be attributed to your firewall or security applications, which may be blocking your ability to connect to the ArenaNet servers. We recommend disabling your firewall first and seeing if this fixes the issue. To quickly eliminate whether or not background applications might be interfering with the client, you may want to try disabling background processes which is outlined in the KB article below:
You may also want to check to make sure that you are running the installation as the administrator.
Beyond this, please submit a support ticket to our Technical Support Team so that we may gather some more information from you in order to locate the cause of this issue.
(edited by Moderator)