laptop, no sounds

I have an Advent 7016, mainboard=American Megatrends Inc. N251s6...no rescue/back up discs.

On installing windows xp pro, my device manager showed a problem with sound.
I clicked on install driver and chose to allow a microsoft driver..this installed and device manager showed I had no problems, though I still didnt have sound.

Eventually I found out I should have had SIS 7012(according to an advent support forum)...I downloaded and installed these and finally had sounds.

However three days later the sound, even at full volume, was very low and then it disappeared totally.

It still appears to play, and as far as I know weverything is enabled. but I hear nothing.

I tried going into device manager, and uninstalling sis7012 and then reinstalling, with no luck.

Can any one help me regain my sounds?

Thanks.