New Computer Restarts Randomly

I have just recently built 2 new computers, same exact components about a month ago. One of them works great, the other restarts randomly usually when installing something. The windows error files are mini.dmp and sysdata.xml and when I send the error report it tells me thats its a hardware error with either : CPU, Motherboard, RAM, or Power Supply. I have replaced all of these and still have the random restarts. I have monitored the temps of the Board and CPU and they are constant. I have run memtest86 with no errors. I don't know what else to do. Any advice would be greatly appreciated.