open ur realtek sound manager ....in the speakers section there is advanced settings ...click and then select play two different audio streams for front and rear speakers
This setting does not deal with stereo upmixing; it has to do with whether the rear-panel audio outputs are automatically muted when you plug headphones into the front panel headphone jack.
This mostly seems to be an issue with motherboards that use Realtek onboard audio. The Realtek HD drivers for Windows 7 do not currently appear to offer a stereo upmix feature, which is what allows 2-channel stereo to be played back on more than two speakers. So even if the rear speakers are recognized in the test utility, when you play normal stereo audio sources, sound will only come out of the "front left" and "front right" speakers (unless you use a program that has its own upmix functionality). This seems likely to be a bug: some of their earlier drivers offered this, and the drivers offer many *other* modes that upmix and modify stereo audio output, just not a simple surround upmix.
To fix this:
Ideally, Realtek should add back in the "surround fill" option that was there in some of their other (non-Win7) drivers. If that option is there, just check it and you should be set. You might want to try the latest drivers from the Realtek website to see if they have fixed this. As of 7/21/2010, the latest drivers (R2.50) do not have this option, at least in Windows 7 64-bit.
If that option is not there:
They *do* have another mode that will do this, but it may slightly affect the sound output. If you go under the "Sound Effects" tab in the audio manager, changing the "Environment" setting to "Room" will effectively cause a stereo surround upmix. (All of the modes will do a stereo upmix, but most of the other ones apply various effects that will make your music sound terrible. This one is close to neutral.)
Another option -- if your motherboard's chipset supports it -- is to use Dolby upmixing. This *also* may slightly affect the sound quality, although probably less than using their effects panel. To do this, go to Control Panel->Sound, select the "Speakers" output device, and hit the "Properties" button. This should open up a tabbed window with a bunch of settings. If you have a "Dolby" tab, go to it and check the "Dolby Prologic IIx" checkbox (or whatever option is there). This will remix stereo sound into 5.1 or 7.1. If there is no "Dolby" tab, then your motherboard does not support Dolby upmixing.
Another possible solution is to set all the jacks where your speakers are plugged in to "Front Speaker Output". This will cause the driver to send the same 2-channel output to all the speakers. However, this will break anything that tries to play real 5.1 or 7.1 audio, since the side and rear audio is then not going anywhere!
Realtek also offers a utility on their website called "3D Soundback". This may be helpful, although it has to be configured on a per-application basis. It is also designed for Windows Vista, so it may not work properly under Win7.
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