My buddys xbox had the 3 red lights and we fixed it by putting new thermal paste on the CPU and GPU, after we cleaned them up, but we didnt do the X-Clamp fix, so after we got it fixed we started it up and it worked fine for a few minutes, then we were going throught the dashboard and the screen turned to like a lime green and then went black with little white lines through the screen. Is this caused from not doing the X-Clamp fix or what? Please someone help Please!!!!!

Thank You
ohh but i still can hear sound when i turn on the xbox

Xbox Quick Repair Guide