From WIKI

Guild Wars client is designed to download the streaming updates in the background or when needed, in a way that will not much interfere with the user. This, however means that when a large-scale update is released, users may be required to wait while necessary files are downloaded and decompressed upon entering a new zone. With this switch, you can force the client to download and decompress all the pending updates on start up so you will not have to wait while entering a new area or mission.

The Game, when started with this switch, will exit immediately after it is finished with the download and decompression. Do not use this switch in your regular game shortcut. Make a new shortcut and name it something like “Update Game”.

by taking the following steps:

- right click on your GW program icon and make a shortcut.
- right-click on this shortcut and bring up Properties
- in the Target box, do not erase what is there, but after it, type:
-image
so it looks like

“C:\Program Files\Guild Wars\gw.exe” -image
Its really a simple thing to do.

BUT even with a hi-speed connection it took a couple of hours to download all of the maps!