Long story short, my little cousin turned on the computer, don't know how long it was on but when I found it there was no display. It's a compaq presario originally had windows ME but it was upgraded to XP.
Since I plugged the screen to my laptop and it worked fine I moved on to find the issue on the computer.
Reset the mobo battery, no result.
This computer has a dedicated video card and no integrated video card so no way to connect the monitor directly to the MOBO. I took the video card off, cleaned off the dust and put it back on to no result.
Took RAM off and put it back on, nothing.
Disconnected all drives except hard drive, nothing.
Then I remembered I have a POST card so tried it, the code read "no-C" which is no CPU detected so I opened the computer, put some new thermal paste on the processor but nothing changed.
Then I tried a different power supply and tried to turn on the computer, the red "Compaq" screen appeared but it froze there and didn't do anything else.
I turned the computer off, waited a few seconds, then back on and again no video output.
I got a couple of computers at home but none could fit in that video card to test it. At this point my question is, is there a way to know if it's only the video card malfunctioning and not the whole MOBO?
Any other suggestions to repair the current problem are very welcome!