Have to re install audio driver every time I turn on laptop

Hi everyone! My laptop was working fine until I updated my graphics driver about two weeks ago. After rebooting my laptop for the changes to take effect, I noticed I wasn't getting any sound from the built-in speakers. Then I spent some 45 minutes browsing the Internet, and the speakers suddenly worked, without doing anything, so I thought the problem with the sound was fixed. Nonetheless, the next time I turned my laptop on, the same issue happened again and this time waiting didn't work. I figured it had to be the audio driver and checked for updates, but it said I had the most updated version. I tried uninstalling the audio driver, after which I got a notification in the taskbar reading something like: "controller installing" and after a couple of seconds "your device is now ready to use." (I did not install the driver again, I just uninstalled it and immediately after that I received the notifications). This happened about two or three times. It has gotten worse since, because now I do have to uninstall the driver and install it again manually to get sound from the speakers, and to make things worse today I discovered the mic doesn't work!

I've also had problems getting my laptop to play sound through headphones and recording sound with both the built-in mic and the one in my headphones. Also, after installing the audio driver (and rebooting and getting sound), I stopped using the laptop for about 30 mins, and when I came back the sound had stopped working despite the fact the laptop hadn't gone to sleep mode. This issue with the sound is really driving me crazy! I need help, please.

I also tried rolling back the graphic driver but the option to do so was grayed out.

I have a Lenovo G400S running Windows 7 ultimate 64 bits. Graphics card is Intel(R) HD Graphics 400. My speakers are Conexant Smart Audio HD.