I have a dell desktop. 400mhz. I install a modem and it started just right. I restarted the system and it started right again. I restarted it again and it started just right. I shut it down until I was ready to used it again. I started it 1 hr later and the computer would not say anything. I checked the power cords and I also remove the the powersource and put it back. The system does not nothing. Do anyone know what could be the problem ?