Hey I had the same problem and heres what I did to fix it
1. In the search bar by the Windows start button type Device Manager, when you see it, click on it.
2. Find Display Adapters and double click on it, and there you might see Microsoft Basic Display Adapter.
3. Right click that and click Update Driver Software.
4. Then click Search automatically for updated driver software.
If step 4 doesn't work, then,
1. Right click it again, select Update Driver Software, but this time click Browse my computer for driver software.
2. Then click Let me pick from a list of device drivers..., then you should see Intel(R) HD Graphic 3000 in the list.
3. Click on that, then click Next. After that it should install it, the screen will go off and on, click and your Fn key and Brightness should work
4. After that it should install it, the screen will go off then back on, click Close and your Fn key and Brightness should work.
If that doesn't work, try restarting your computer
I hope this solves your problem