Here are the steps u need to follow:
1) First install Advanced Sytem Care Free.
2) Reboot ur computer and start with safe mode (right after you reboot before any windows screen appears, keep pressing F8. )
3) After it boots at Safe Mode, go to control panel, add remove programs , look for your sound driver you installed, presumably RealTek drivers. Remove /uninstall it, by just clicking on it.
After it removes it, will prompt to a screen asking to reboot, do not reboot. Say no, for later.
4) Then, go to Advanced System Care Free, which you can find under start, programs, etc...
5) Run it. Spefically run the Windows Maintenance which it's the top circle option that should clear your registry files of audio you uninstall. You may have to run it once or twice until you see no more errors found in registry.
6) Reboot, again make sure you hit F8 to go to Safe Mode.
7) Go back to Advanced System Care Free, run the same thing again. Clear all the errors until no registry errors found.
8) Install the Realtek driver. After install will ask for reboot.
9)Computer is rebooting, do not hit f8, let the windows run normally, you SHOULD hear the sound.