No offense here, but if you don't know how to get into the BIOS, you need to be VERY careful while in there or you could cause your system to not boot.
Time to look at your system documentation online about entering the BIOS and what settings are there regarding sound.
Generally, when you start any coputer, it shows something like "hit F2 to enter BIOS" or something like that. It is usually F1, F2 or DEL key to enter BIOS.
Then you have a bunch of menus to go through and somewhere there is usually an option to have "onboard sound" enabled or disabled.
If this unit is under warranty, I'd highly recommend that you call IBM/Lenovo tech support. If not, just be careful once you get into the BIOS. When in doubt about changes you made, there is an option to "Exit Discarding Changes". That will undo anything you have changed.