No Audio in Vista

hi all newbie here can anyone tell me how to fix the audio in vista just bought this comp win vista 32 bit home premium acer athlon with realtak hd audio…

k… windows player and center no sound,, wont play dvd
although speakers plugged in correctly volume turned up.. codecs are installed,,, shows as working..
windows sound test no sound no sound from net…on anything

and that is just for starters

so the cd player wont work the dvd player wont work… even the windows basic sounds wont work…. any one help

only 3 wks old… over 7 bills and dont run correctly…………