No sound

my system crashed a few days back ... and i formatted the drive and reinstalled win xp home edition along with the drivers later on ... nut now i have a problem there is no sound coming and it says no device found on the soun and game controller option in the control pannel ... altho i have installed realtek high definition audio....... plz help.. in the properties of realtek device at the driver tab on top i've noticed that the driver provider bar , driver date, driver location, all is not assigned and the driver signer says not digitally signed ... what do i do i guess because of this it aint coming plz help