Windows – Install windows7 on Macbook Air – no sound

I installed Windows 7 on Mac book air, but now there is no sound.
I googled similar issues- one of the finds came out that I have to install realtek drivers, which I did, but still the issue persists.

I downloaded the realtek driver from this post: http://www.fixkb.com/2011/05/no-sound-on-macbook-running-windows-7.html
(the solution section).

Here is screenshot from device manager – what is bugging me is you can see there are two entries in the Sound category, one showing a warning sign.

Can anyone help?

strangely if I use headphones there is sound.

Here is some info on MacBook:

MacBook Air (11-inch, Mid 2011)

ps. this is not speaker issue

pps. I don't use bootcamp the only OS on my computer is Win 7 now.