I know someone has already chosen a best answer but its the wrong one.
Here is how to fix your Windows 7 SM Bus Controller issue with ASRock Extreme (mine is 6) series motherboard.
0.1a - Go to Start, Right click the word Computer, then click MANAGE.
0.1b - Click on Device Manager. You should see SM Bus Controller and thats all under the section of unknown devices. It will have a Yellow placard and Exclamation point to indicate drivers are missing.
0.1c - If ANY other devices are listed, right click the icon, and select Install Update, it will go online and I BELIEVE that one of them may be the USB3 controller... for some reason it doesnt install it properly the first time, but gets it the second time.
---Once you have only SM Bus Controller (or tried your hardest to get that way) ----
1. Go to ASRock website for your motherboard, i just googled ASRock Extreme6 and it popped up.
2. Select the downloads section of the site
3. Select WINDOWS 8 64 bit
3a. Yes i know you're NOT using windows 8.. dont care, this works
4. Download the INF file from your nearest country
5. Open the INF folder and double click SETUP
6. Let it install, notice it says NOTHING about windows 8 in the install? Thats because its just chipset drivers.
7. Click next once it has finished installing, and thats it. Now to check that SM Bus Controller is now gone from unknown devices.
8.1 - Go back to the Device Manager window (or repeat steps 0.1a-0.1b)
8.2 - Check to see that all devices are now found.
8.3 - Feel free to share with your friends.