I have just recently installed Windows 7 64-Bit on my computer and there's no sound. The drivers that were installed on it through Windows Update is: Realtek AC'97 Audio. Whenever I play a song or something you will see the green bar move up and and down but no sound is produced through my speakers.
Since your symptoms are the same, might try the fix I suggested to another poster that worked for him.
In the playback window (posted in your last screen shot) select the Digital Output then select "Set Default" then select "Apply', then re-select the speaker output select Set Default and Apply.
Under the configure button make sure you're set to the right speaker setup, stereo?
Under the properties button you can run a test.
Ap