Monitor gets no signal

Hello,
I am having a problem with my monitor, i recently replaced the HD on my 5yo systemax computer and cleaned with air duster. Once i replaced it ,the computer was operational, i was able to reinstall windows and other software. I took it to another location and set up and thats when i discovered the problem, no post and no monitor signal. Tested the monitor on other computers, worked fine and vs on the tower. Anyhow i purchased a new video card and it still didnt work. I tried the suggestion to unplug everything and hold pwer button for 30 secs and reconnect the pwr,monitor, keybd and mouse. I did get a post signal, however my screen is still blank, no message, no way to get into bios. The pwr light on the monitor is steady as oppose to blinking when it was blank, but blank screen. What do I do?


Please let me know if you need additional info,
Nat