Well i did everything u said. i also replaced the video card with another and it still didnt work. i also tried another monitor in my room and it says "PLEASE CHECK SIGNAL CABLE"
i just got 1gig of ram and after i installed it i turned my computer on and nothing came up on the screen. i know its not the video card or the monitor because if i press ctrl + alt + del it does reboot and when i press the power button when it first turns on it doesnt turn off i have to hold it...