Unable to initialise 3d output

So today I closed GW and rebooted my PC and then logged in again (because my video driver still has a problem if someone else logs on to pc). When I started GW I got this message:-

Unable to initialise 3D output Please verify that you have installed DirectX8 and an updated video driver

Click the URL below to open a webpage with more information

http://www.guildwars.com/support/en-...ationerror.php

Now bear in mind that I am totally non technical....why does GW suddenly not work and do I really have to download MS stuff I dont understand when the game worked perfectly well an hour ago? what changed?

Is direct3d enabled? If not, enable it, also, what graphics/video card do you have? More information would be nice.

I don't know and I don't know how to check but if GW was playing happily just before I guess it must be?

Graphics card is a radeon HD4350 and it has been nothing but trouble .....

what other info is relevant?

ty for answering