Hello all. Just going to skip the back-story here; my desktop PC stopped working right after I replaced the motherboard and case for it. At first, I was using a Micro ATX Gigabyte motherboard for the computer. Since this was micro, I decided I needed a full sized ATX motherboard. I buy a BIOSTAR TH55XERCH LGA 1156 motherboard, and a new Antec 300 case to go with it. I install everything and my computer has a hard time starting up. It takes about seventeen attempts to get it to start. It finally starts and everything loads correctly. During the use for the next three weeks, I experience random crashes and windows freeze ups. No BSOD and no warning. The USB power for my keyboard and mouse froze; I could not turn it off. I would have to unplug the desktop and plug it back in again to get it to start. This stopped happening for a while until I went into my motherboard and checked the voltage for the Vcore on my Intel i3 540 Clarkdale. It was set to 1.26 volts. After studying a little, I learned 1.24 would be better. I set it to 1.24 volts, save the settings, and exit the BIOS. Now I hit the power button and the computer comes on for a quick second and shuts off right away. I troubleshoot a lot, ask other opinions, and come to a conclusion that the motherboard is bad. I get the RMA ready for it and buy a new motherboard. This time, it is the ASUS P7P55D-E LX motherboard. I get the motherboard, do everything you are supposed to do to get the computer working, and push the power button. It does the same thing over again; power on, power off half a second later. This motherboard says that all the power is good by lighting up a green LED light. I followed the guide on the Biostar website for overclocking my CPU, checked my ram, unplugged my HDD and tried a HDD free boot. Still a power on, power off. Please guys... I really need help getting this to work again. I've already spent a lot of money and would not like to waste anymore by buying something that will not fix the problem.