The Guild Wars team has added a nifty new feature to the UI log in screen. There's now a button called "Test My Computer" that will....er....test your computer. Here's what else it does:

 

Update - Thursday May 29
Support Features

Added the "Test My Computer" option to the login screen. Clicking this link launches a diagnostic test that measures:

* Adapter settings
* Network connections
* External address
* Server connectivity
* Network paths
* DirectX diagnostics