what specific file should I locate in the MSConfig that is related to the audio/sound? Sorry, I'm not that expert in computers.

I usually does the windows update if there is available update to enhance the windows of course.

What do you think is the audio driver that I need to install that is compatible with my laptop?

I have downloaded the link you gave me then install it and restarted the laptop but its still the same, I have no sound and red mark with white cross is still shown in the speaker icon on the bottom right of my screen.

yes, I already tried system restore but it's still the same

thanks paupau but I was able to bring back the speaker again and its working fine now.

What I did was, after shutting down the laptop, I bring the laptop outside the house since I am connected via wifi thru the router inside my room.
Viola! while it is opening its windows logo, i heard the start sound then entered my username (already by default) and password to get inside the windows.

Viola again! there is a sound and the red mark on the bottom right of my speaker icon is gone.
When I check the device manager, the sound, games and controllers are there and the realtek high definition audio since they are missing before. I just have to remove my internet connection, piece of cake!

I hope for those who experience this, try this, remove the internet connection after shutting down like if you are connected thru wired just remove it from the laptop or if you are connected via wifi just close the wifi button in the laptop or go out in the house where it cannot detect the wifi if you don't want to turn the wifi switch off.

Some suggested to put the laptop in sleep mode instead of restart, then it will install the drivers automatically that is missing in your laptop as they say. It works for them but not for me. The only solution for me is to remove the internet connection.

Hope this helps.