Ok I got a problem with my desktop, sometimes turn on and sometimes it doesn't. The problem I have is that sometimes when I connect the power cord objects connected to the computer having lights also start flashing and it put a weird noise to the speakers, when this happens the computer doesn't turned on. Other times I connect the power cord and all the lights stay calm, in these cases the computer turns on and everythings works fine.
These thing happening is really weird, at first I think it was the power supply but I changed and still the same problem. The only way to use the computer is to never turn off once you get it working... so I was wandering if someone got any ideas?

You could have a short in the cable that could cause the problem try a new powercable