Hey guys, I have had this problem for a long time with my PC now, and it has been preventing me from putting in any decent graphics cards. What has been happening is, I've put a graphics card in, played a game, then after around 10 mins of gaming, the screen freezes and the sound just goes over and over and over. I've had to reset my PC many times because of this problem, and I'm wondering what is causing it. However, when I only use onboard graphics or low-end graphics cards, everything is fine. I can game for ages and nothing will happen. For example, here's me specs when it WILL crash : AMD Sempron 3000+ 1.8Ghz 768mb Kingston Memory (not sure about the motherboard) 250/300w PSU... I think its 300w max Ati Radeon 9550 80gb Seagate HDD Take out the Radeon 9550, and it works fine. For example, I used a Radeon 9200SE and it worked perfectly, no problems. Also, when I used the higher-end graphics cards, and sometimes even with the lower-end ones, it gave me an alert during games that "Your gpu was not responding to driver commands. It has been reset..." etc. This gave me the idea that not enough power was running to the cards.. This is just an Acer T135 that I have moved to a new case and stuck some more RAM into. All I need now is to be able to put higher-end graphics cards in, like the nVidia 6 and 7 series, and I'll be completely happy. Please help. What do you think the problem is? It isn't temperature...my case has a huge fan at the front and two fans at the side, blowing air directly onto where the graphics cards are, so it surely isn't. I think it's the power supply. Anyone think they know what it is?