After formatting Pc, all the graphics files stop working if the required drivers are not installed. If at all you have a driver cd which you must have got when you purchased your Pc then you can install drivers from that cd.
But many times driver cd is not available or it gets corrupted. So in that case one solution is to open your PC and see the chipset number which is given on your motherboard. But if you are not a computer professional then things can become difficult. So in that case you need to download one utility from Intel
After downloading just install it and it will tell you what is your chipset number. After knowing the chipset number you can download the required drivers from the same Intel website or by doing google search for those drivers.