I am having HCL intel 845 board. in that audio is not working. actually I formaated my Pc. unfortunatly i misplaced the HCL baod C.d . I m having the c.d of 845 intel baord but that not of HCl. everything is working fine but Audio driver is missing. I tried to installed many driver like:- Ac97 , Realtek, alc880 ,AD1980. but sound still not working..

Is necessary to Download that drivers from HCL board Driver C.d Or I have to buy a new sound card ?

I suppose you have Windows XP, does it show Audio Device in Device manager ?
If yes then your on-board audio is fine, you only need right driver. Most probably you have AC97 driver.

I suggest you to uninstall any previously installed audio driver and download fresh from Intel website and install. (Simply run the setup came with it)
Download AC97 Audio Driver

Ya there no error showing in the Device manager. Its showing the audio device there. let me try this one . If i face any problem I came back

Thanks for the information.