HELP-No Audio Device

hey guyz.... i have a problem here- in control panel in sound & audio devices i get 'no audio device' & i cldnt here any sound. der ws sum problem with my SMPS later. i installed my frnd's SMPS temporarily. den i cld properly here the output. now i put a brand new SMPS. but still nw i hav d same prob. i cant here the audio. n get d same 'no output device'. wht shld i do???? i have drivers installed. i use windows XP SP3