You should of got all the drivers on a Cd, or a dvd for the board.
If you did a self build.
If not and it was a pre built system then the drivers will be found on a partitiion of the HD along with and Image of the old Os.
Normaly you get a recovery cd, or you have to make one through windows.
If that is not an option, you should be able to find the brand name of the board and its model number from the bios post screen. Or you will have to open the side of the case up and you will find on the main board it`s self the brand and the board model number.
You will then have to use another working pc to google the board number for the drivers.
Once found download the whole set for the board and stick them on a CD or something.