How do i fix my audio on my computer?

I have A windows XP computer. I went to Geek Squad about 2 months ago and they gave me new speakers and said my computer needed a new sound card. i got it back as good as new. My sister fiddled with some cords in the back of the computer and now there's no sound. i hooked everything back up yet there is still no sound. My friend suggested to download a sound driver. is that right. i dont know how. but i do know the sound card was a sound blaster Audigy one. what do i do???