lenovo 3000 y400 audio problems? Fr singapore

i am a computer newbies.i just bought this notebook last month. after i had used it for about 7 days without any audio problem. one night, when i was listening to music, suddenly there was no sound come out from my earphone or the speakers.
(os vista home basic and realtek high definition 5.10.0.5324 audio driver software).
i did send my notebook to the service centre instantly the next day, and they kept my laptop about a week without getting the audio problem fixed. the reply i got from them was somewhat unclear. and they gave me a feeling that they were not very sure about the problem. they said the problem was probably caused by imcompatibility between a chipset and the os. they added they had tested with os XP,(i do not know how they carry out the test), there was sound from the speaker. and they asked me to collect the notebook home first and wait about 2 weeks time for the production of an improved motherboard , which they claimed could solve the problem.
last night, i tried to uninstall the preinstalled audio driver program, and then reinstalled the audio driver from the CD that was given with the purchase of this laptop. a surprising doo sound was heard when i accidentally clicked on the close tab halfway through the installation. does this mean the speaker of this laptop are working fine? if it is working fine, then what should be the problem that causes no sound from the laptop? how credible was the reply i got from the staff working in the service centre.
till now, my laptop has no sound at all with audio driver software installed, a doo sound during installtion of audio driver software when clicking on the close tab.