No audio

Hello,
my computer was recently reformatted, but then after that, my sound device wasn"t functioning anymore...Under sounds and audio properties- I have no volume control, no sound playback devices, no sound recording device,no MIDI playback device. I have no sound with external speakers, mic, and headphone.. my audio and video files wont play...i heard its usually the case after reformatting..is it a hardware or software problem?? how can i fix it..??
i dunno much bout computers..
need help.
thanx