Hi,
Already many of our friends have faced the same problem which am facing right now.
My taskbar changes its colour into grey and sound gets disabled.I used malwarebytes antimalware but of no use can any one help me ...
reply as fast as possible.......

This happens to every login user to that compputer. Login with different user and try it.
For sound problem- Try to install the sound drivers

This happens to every login user to that compputer. Login with different user and try it.
For sound problem- Try to install the sound drivers

I have installed the respective drivers realtek hd audio codecs . When i start the computer every thing will be fine but later task bar colour changes and the sound is disabled

Have you tried Safe Mode with Networking?