Hello Janbro, and welcome to TSG.
1) Are we safe to assume that you have tried fully shutting off the computer and turning it back on?
2) If you are using a video controller board plugged into the motherboard and the motherboard also has a built-in controller, have you tried powering up with monitor connected to the motherboard's video output?
3) Does you motherboard use POST status LEDs or Beep codes to show the power-up status? If so, is the motherboard indicating a normal power-up?
4) Do the monitors show any error messages during boot up?
Beyond that we will need some more information about your hardware and operating system. Please provide a parts list of the major components in your computer, including brand and full model numbers of the motherboard and any video card. Also what version of Windows are you running?
