Hi guys, Im having trouble on my desktop for a week, one day when i turned on my pc, after running it for 30mins, the monitor turned black but the cpu has lights turned on. I reset it, then it asked me to open it on safemode or normal windows, i chose normal windows and it started. After a couple of minutes, the monitor turned black again. I've tried to turn off and on the monitor switch but it didn't help. So it makes me wonder what the problem is. I press the reset button again but I have a suspicion that it might be the monitor that has a problem. when the window started, I open my media player and play continuous songs, after a minute, it turned black again BUT the song continuously playing, then after a minute the song stoped! So im am sure t is not the monitor. I tried to open it in safemode to do some investigations, and it was not shutting down even for an hour. I made some diagnostic tests and all hardwares have passed. I've tried to re-seat the memory card and video card but when i run it in normal windows, same thing happened. I had a suspicion that it could be virus, so i reformat it 2days ago. after reformatting, same thing happened, but this time lines started to appear on the screen, the graphic looks weird, it almost have 8-color display on it. I've checked the video card in device manager, and it says it is not functioning. So my video card got broke. Now i am wondering, during the past few days, the graphics look good, but as i am trying to troubleshoot it myself again and again, the video card is now broken. As i remember 5 days ago, when i made a dell diagnostic test for hardware parts, everything has passed, but now it is saying that my video card is not functioning. Any idea that its really my video card got broken, or are there other hardwares mulfunctioning causing the problem and hit my video card? What causes the video card failure? I do pc gaming, I do 3d modeling, but i use my machine for an average of 4hrs a day. It was so dissapointing because my desktop is just 15mos old. It is Dell XPS 420, with nvidia geforce 8800gt 512mb ddr2. And unfortunately the warranty is expired. Any help would be really appreciated. Thanks in advance!