MichaelStanding will tell you to throw your computer in the bathtub and try it...don't listen to his stupid comments. He's bound to be banned soon...
Try reseating your CPU, messing with the fan might have somehow made your mobo think that it is removed or something.
You are sure your monitor is plugged into the wall still? I've knocked my cable b4 workingon my PC
Does the monitor work with another computer? That's the first thing i would have checked.
Just to be safe, i'd reseat the CPU, RAM, GFx card, and unplug mobo from PSU. then plug it all back in and power on the PSU again and fire her up. If that doesn't fix anything then i'm stumped for now.
Double and triple check your connections. if it's plugged in reseat it, if it's hasn't been messed with reseat it all the same. sometimes computer can be retarted if you knock the CPU just a tad accidentally.