Help! My Hp z440 wont show anything on screen, fans turn on, but there static noise when turn on.

[Jake_202]

Help my workstation, HP z440, wont show anything in screen. Before that it boot it up and I could access the BIOS. I changed some settings in the BIOS.The error then was the 6 beeps and I fixed it by pressing the CMOS button for 5 seconds. Now the computer does not beep, but it does even show anything on screen (no booting or even displaying the logo of HP), it is just a black screen. Moreover, when I now power on the computer, it create static noises and it seems that motherboard does not give any external power (like mouse and keyboard wont work, but the internal fans of the computer (CPU fans and video card's fan turn on). I need help, I don't what to do to fix this.

My computer has 8 GB of ram, no hard drives and 700W power supply. The video card is the one that came preinstalled in the computer, 

[Jake_202]

I fixed it by myself. 

[Jake_202 · Accepted solution]

After a few experimental tries and ideas, I just went with taking out everything clean it all out and reputed everything (had to replace the video card with a new one) in its rightful position (new thermal paste in CPU). Then I holded the power button for 20 seconds and voila no static noise and it booted it just fine.