ok i asked tomshard a few days ago witch gpu i should get a while back they said i should got gtx 650 with my budget and system specs well i just got it and took my othe gpu out and it works so it seems but in the operating system it says i dont have one installed and i know the gpu says i need a 400w power supply but i only have 380w but some pepole said i dont really need that becuase it dosent really run at 400 w and i do light gaming.....i dont understand whats wrong HELP