I bought this computer :
Lenovo - Desktop - 6GB Memory - 1TB Hard Drive
Model: H520 - 57317327
But I installed a new PCI E video card - 2GB , DDR3 PC3-10666 (2 sticks of 4GB) RAM , and a VGA Cooler fan.
When I went to turn on computer , it just beeped non stop .. until I turned it off.
I tried different power outlet , same problem.
Removed all new items , went back to how it came from store .. and it came on fine.