Why is there no sound driver

hey,

well, i had an HP laptop that i got from my brother, after abt 4 yrs it just stopped comming on, the lights would blink and everything, but nothng wud show on da screen,......but thats not the problem, i currently have a Haier laptop which was working perfectly fine and my tecnician dd something (changed the exchanged the hard drive with the hp computer) at first i was like ,whooo all my documents are back, but no i have no drvers for wifi, sound and God knows what else, mostly i ned the sound, cuz i hav connected a lan cable and im gettin ma internet conecttion, Please Please PLEASSSE!!!!!! HELP ME!!!!!! just the sound driver info wud do plllz help me