No sound

Hello,
my name is dexter ok the problem is that a few days back my comp crashed and i formatted it and reinstalled the os and the drivers tooo .... but still there is no sound im currently using windows xp home edition service pack2 realtek is installed on my machine but when i open the sound and game controller option from the control pannel it displays no device found and also what i noticed was that in device manager i doubled clicked on soung and ganecontroller option where it opened where i doubled clicked realtek high definition audio but when i clicked on properties it displayed a window i then clicked the driver tab on top and found out that the driver provider bar says unknown and driver date not assigned then driver location not assigned then driver signer says not digitally signed .... how do i go about this pls suggest