moniter has no picture

ok well me and my freind traded computers and when it was on the sound wasent working so i unpluged the sound cord and pluged it in a diffrent slot that dident work so i tried again and somehow i acedently disconected the sound card and then my moniter stoped showing a picture and after turning the computer of and then back on it still wont turn on but i have tried diffrent cords diffrent outlets disconectine and reconecting the video card and memoery and i have run out of ideas please help