Please help me out with this, My computer won't boot! How do I fix this?

turn off your pc, unplug it. make sure you put everything back in right. take your video card expansion card out for example and put it back in. It looks like your expansion card is not set right in the slot. or your monitor cable is unplugged( but you would no that). reboot the PC and it should be back to normal. You might be asked if you want to load windows normally just select that. see what happens. Your mother board, cpu, hardrive(you can here it running it is good) and memory card are good. Otherwise your pc wouldn't run at all.