I built my first PC in May, and I had no problems putting it together. However, I had a really stupid moment where I plugged in my HDMI cord and I could hear my PC working, but no screen. I tried for about an hour to figure out if everything was plugged in correctly, which everything was. It turned out I plugged my HDMI cord into my motherboard and not my GPU. Since my motherboard and CPU don't have integrated graphics I can't use my motherboard's HDMI slot. I felt so dumb after I realized I plugged in my cable in the wrong HDMI slot.