I have a Dell XP5 2710, which had an HDD installed. Sometimes the PC would not turn on at all, just a black screen, but the fans would run. Sometimes it would run normally. Today I installed an SSD and plugged in a Windows USB, but now I only get a black screen with the fans running. When I reinstalled the HDD, there was still only a black screen with the fans running. I also tried a hard reset by holding down the power button for 20 seconds and pressing various function keys. Sometimes the 3 LEDs would turn on.Please help;(