I have hp all in one desktop and when I try to turn it on, the power light is showing but computer isn't turning on and screen remains black. Recently I got replaced my motherboard from HP one of their technician came to my house and swapped the motherboard and I asked him whether it is a new motherboard or used one and he said that it is refurbished motherboard as the model of all in one you're using it's manufacturing has stopped, so I said okay after installing the motherboard I also should upgrade ram of it so I put one more kingston 4gb ddr3l 1600mhz stick in it and now I have 8gb of ram it works flawlessly. Now every time I shut down the computer, it won't turn on, the power light stays stable but no sound of error or anything, it won't even turn off on it's own. And when it won't turn on, I unplug all the cables, put it down and open it up, from there first I remove all the ram sticks and try to boot it up but still no luck, and next when I remove battery cell on the motherboard and unplug the sata cable of hard drive and unplug the power cord, I try to hold up the power button for 15-20 seconds and then I put everything back in, BOOM, it boots, and I plug everything back in and close the case. Now after it boots up, everything works now when I use it for like 4-5 hours, then I shut it down thinking that problem won't come again and try to start it up next day, the problem came back same thing happens again. Any help would be greatly appreciate. Thank you and sorry for bad english.