Out-of-date drivers and operating systems can cause a variety of issues, and are one of the first things to check when a game is having problems.
Requests for date and time of when a CD key was redeemed
Troubleshooting steps for disconnection issues when playing Diablo III.
These keys require a full version of Diablo III and a game account in the appropriate region.
Troubleshooting steps for latency problems in Diablo III
Troubleshooting steps for performance-related problems.
Information on what to do when a game update is stuck at 0 B/Ss
How to install a Blizzard game you already own on a different computer
How to reset in-game options
Troubleshooting steps to resolve performance problems in Diablo III.