My computer is connected to my receiver using an HDMI cable and the DVI to HDMI adapter I received with the graphics card - ATI Radeon 4870. On my old system (Vista 64 bit) everything worked well, and the playback devices showed the HDMI output transfering 5.1 and it was indeed doing it (I could hear 5.1 audio out of the speaker system).
I recently installed Windows 7 64 bit, and installed the Realtek HD audio driver R2.14 which enables me to select 5.1 audio in the playback devices configuration window. this is the same procedure I did for my old system.
However even though it shows as if the output is 5.1 audio, it only outputs stereo. That is, when I test the rear speakers (click on their picture) the front speakers are playing. There is nothing wrong with the hardware (Computer, ATI card, receiver or speakers) since everything worked well on my old vista system.
How can I change it to true 5.1 audio?