So I got a cheap rebuilt compaq 4300 pro desktop. It is SLOW. So I bought a cpu which is compatible (Intel® Core™ i7-3770S (3.1 GHz, 8 MB cache, 4 cores) and installed it. When I plugged it in I got three beeps and red lights (no white) and the screen did not come on. So I reinstalled it and this time green lights and the fans came on but not the monitor or key board or mouse. I read that I should have updated the bios first so I reinstalled the old cpu and the same thing happened- green lights and fan but no screen, mouse, or keyboard. I tried unplugging and holding the power button for 10 seconds but all to no avail. Please help!!!!