Cpu on's but no signal to monitor

hi, my cpu on's but my monitor has no signal. i hv tried all tricks. changed my vgi card n hdmi card 2 times, rubbed the battery in mother board, cleaned my ram and its slot, cleaned my graphics card, pressed d power key for a long time with no power supply, i hv done all this still my computer wont turn up. wn i on d cpu d red light keeps on continuesly and wont blink. as my system was slow with 4gb ram i wanted to format it. wn i insert a new vgi card only 1 time d systems on's and it says recovering files and it jus get stuck their. hope some one understands my problem. plz guide me as wt to do. i am plucking my hair coz f it.......