sound issue on macbook pro 13 inch version 10.7.3

hey guys its been tough switching to mac..but fun though...the thing is, i am a dj and i observed i had a sound issue on my mac partition after having played music on the windows drive using an external usb sound card. when i switched back to mac os, i noticed i was not getting any sound out put, yet still all the settings in system preferences are good, and my volume is up. i try to restart many times but the problem is still there. what i do notice is that when the come mac starts up i am still hearing the chimes sound ...so which means to me it might not be a major problem but how eer i just cant firgue it out. help needed:Blushing:

Have you got something plugged in to the speaker socket ? It will recognise both wire and fibre automatically and switch accordingly to whichever is present.