When i power on the pc i get these (1 long and 3 short beeps) and the gpu starts for a while and stops but the cpu is still running and the boots to OS, to make the gpu run i have to swap the RAM slots about 7-8 times and there is no definite pattern or slot ,the gpu starts running randomely at 8th time when i swap the sticks....... I already have replaced the gpu and mobo under warranty.............. pls help