My initial problem was that the computer used to reboot continuously at random times with no message in the event viewer. Also, it used to do continuous restarts one after the other. I flashed the bios but the problem remained. A couple of days ago, I replaced the power supply with a bigger 400 watts (from 300). Now, it seems more stable and does not restart continuously, however, it is now randomly shutting down completely. In order for me to switch it on again, I have to turn the power supply switch off and then on again. These problems have started since I installed the WD hard drive. Can you help???