I bought a new PSU and case for my brothers computer, installed them, and the monitor wouldnt come out of sleep mode. All of the fans are running (CPU, graphics card, case fan) and the HDD is working as well. I tried plugging in another monitor and it didnt work either. I put the old PSU back in, nothing, and then the previous graphics card to no avail. What did I mess up/break along the way? Any help or troubleshooting steps would be greatly appreciated.