When I turn on my desktop (some sort of xpc shuttle), it goes to a black screen where you can choose safe mode or windows or last known operational mode (something like that). Which ever mode I choose, the same thing happens. The computer acts like it's starting up (never gets to the Windows screen) and then says monitor is going to sleep, and then it goes back to the black screen where you choose a start mode. It just keeps restarting over and over until I hold the on button for about 10 seconds and it turns off. Any idea what is wrong and how to fix it?