Computer on but displays "black blank screen"

Hi good evening. Please help me fix this up.

Problem:

The pc here starts on. Fans spin, dvd & cd r0m lights which indicates a power, and mother board's led, lights "green", but the m0nitor displays nothing not even curs0r, only a "black blank screen". I also tried omitting the drives(dvd, cd, hdd, keyb0ard, mouse & putting 1 ram stick at a time, STILL NO LUCK!) I cant figure if its b0oting because of the failure m0nit0r display, also i dont have speaker. In the keyboard, caps, scrool, and number lock lights on/off if pressed. The monitor led besides power button, turns also green, where it means that it is recieving signal/power from the cpu. I also checked the cable cord at the back of monitor & at the cpu still the same. Please help me, i wanted to update my bios because the pc is in abn0rmal state. Before this display failure, i re installed the windows (sp3) cause it always c0mes to a blue screen error on different location.

it was a ASUS P4GE MX, 512MB RAM, with an INTEL PROCESSOR. Im quite sure this was a low class processor enough only for its capacity,sorry i forgot the exact data bout that, this was an old model back in 2004

i understand that i am taking a risk to update my bios even though it'll not guarantee an answer to my problem, i dont have warranty anymore i know that. If all else fails il accept it wholeheartedly. Ok back to the topic:
this really frustrates me, please help me, my monitor displays nothing but the pc is "on". Thanks a lot.
Booky20