Dell XPS 630i - Display problems and unable to startup

Hello,

my Dell XPS/Dimension 630i is approximately one and a half year old, and I've had as good as no problems with it.

Yesterday, however, I started the computer and surfed the web for a while, before starting up World of Warcraft. After 5min of gaming, the sound froze and the screen went black, showing "No Signal". I turned off the computer by pressing the "Turn on"-botton, and then turned it on once more. In the first loading-window  (where it stands Dell and BIOS Revision), the area which usually is completely black was full of yellow-green dots appearing in a pattern of four and four. These dots also appeared in the "Microsoft Corporation loading screen". When the "Microsoft Corporation loading screen" was completed, the screen went black for a couple of seconds before a Blue Screen came up, and the computer restarted itself, doing the same thing again.

During the third restart I pressed the "Turn on" button to turn it off. I then turned it on once more, and this time I got the option to run a "start-up problem solver". This program found an error which it could not fix. I now got several other options, and chose to restart and check the memory. As the computer started, the green-yellow dots were now gone. The test found no damage on the memory, and the computer and Windows started as normal. I ran a virus check with AVG Free (none were found). I started World of Warcraft, and was once again able to play for 5min before the screen turned black for a couple of seconds. This time, however, I was able to close World of Warcraft, and the screen went back to normal, and Windows gave me the message "Display driver stopped responding and has recovered". I checked if I had the latest version of the display driver and the display card driver, which I had. I tried starting World of Warctaft again, but this time the screen went black and I got a blue screen even before I could enter my password.

After that blue screen, the yellow-green dots and blue screen have appeared on my screen each time I start my computer, except once, where it started normally. I'm now completely unable to start Windows normally. Secure modus works. I've run the device check from "F12" in the Dell loading screen, and it could not find any errors.

What should I now do? Is my screen (5-6 year old Acer AL1714) broke? Is my display card broke? Can I fix this myself or do I have to send my computer to Dell?

In advance, thanks!

My specc:

Dell XPS/Dimension 630i, Windows Vista Home Premium x64, Intel Core 2 Quad CPU Q9400 @ 2.66GHz , 4GB Dual Channel DDR2 800mHz Memory, Single 512MB Nvidia GeForce 9800 GT