Windows 7: no sound ,Win7-ultimate x86,realtek high definition audio card

hi
i had windows Xp Sp2 for several years and yesterday i have upgraded to Windows 7. everything went fine except for the sound.
i have K9A2 cf-f MSI main-board with on board realtek high definition audio card(i saw the name on device manager it was below of AMD high definition audio device).after installation of Windows 7 when i playing the music the green sound bar is going up and down,but no voice coming out.
here are the work i had down till now:
1.reading several forums before post...
2.checking the plugins,i have switched my speaker to all possible port and its now on green one.nothing
3.installing the last compatible audio driver for Windows 7 from realtek.nothing
4.installing the last audio driver from Msi site.nothing
troubleshooting form Windows 7 and nothing found.
6.try another speaker .no sound
7.disable front panel jack detection from realtec control panel.
8.i had check my speaker it is the default one.
thank u in advance

Assuming you have a Win 7 (or Vista) RealTek driver installed.

Go to the Device Manager, RIGHT click on the RealTek entry and then LEFT click "uninstall". DO NOT check the box to also uninstall the drivers. Restart the PC and when Windows starts it will detect and reinstall the sound. If there were some type of corruption between RealTek and Windows this will fix it.

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Thanks for your suggestion fireberd
but I had done it before and nothing happened , I have uninstalled everything under the sound(high definition audio card and AMD high definition audio device)for several times ,after restarting win 7 automatically recognize them and installing them and it says your new hardware is ready to use and sure it isn’t.

As it shows audio is working, unplug the front panel connection at the motherboard and see if that makes a difference with the rear speaker jack. The "HD Audio" connector should be used for the front panel headphone/mic connections, if you have that. Otherwise the older AC97 can be used.

Also, test the speakers in the Sound Panel, Playback section. Click the Speakers to highlight that and then click Configure. Make sure you have selected the correct speaker type (stereo) and then test the speakers there. I've seen cases where the test was OK but there was some other configuration error causing the PC sounds to not work. At least get a base point - whether or not the speaker test works.

my front panel connection never were connected or at least that's never work with headphone or microphone.i Clicked the Speakers to highlight that and then clicked Configure,the type was stereo and i also test the quadraphonic and 5.1 and 7.1 surround.when i pressing the test green sound bar going up and down but no voice coming out.

Considering all you say you have done, leads to a hardware problem with the sound chip. However, if it worked in XP and now does not that would still say either a driver or configuration issue is causing the problem. You say you have tried two different speaker systems, have you tried a headset in the green speaker jack?

Although drastic, a complete new Windows 7 installation including reformatting the hard drive first and then installing is the next step. Windows will install a generic basic function HD Audio Codec driver, see if that works before installing the correct RealTek driver from MSI (the motherboard vendor's driver is preferred).

dear fireberd
i have tried a headset and no voice comming so i have installed a fresh Windows 7 after formatting drive C.
with both generic basic Windows 7 driver and the one i had downloaded from MSI website there were no sound.

I would suspect there is a hardware problem on the board and if that's the case you will have to add a sound card to get sound.

I didn't look at the motherboard spec's to see if it takes a PCIeX1 type card or if has an older PCI slot for expansion cards.

thanks for your kind reply