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This may allow you to remove SP2. How to uninstall Windows Vista service packs as a troubleshooting step

Try going to search by the start button
Type device manager.
In device manager update the microphone driver, especially if there is a yellow marker by it

Uninstalling the service pack is not going to help as it now means your system is unsafe as it is now unsupported by Microsoft for security updates. Support for Vista SP1 and under ended July 12 this year. I would strongly advise you to reinstall SP2 and update as there have been dozens of updates since then. A few reboots and updates later you may find things start to work as they should,

All this sounds like to me is that a few drivers need to be updated.

Microphone : check for soundcard updates
Media Player Classic is not supported in Vista anyway as far as I know, or at least the original version isn't. Check versions.
DVD drive firmware probably needs updating.

Also check your Windows Update for any updates that you may have hidden.

First thing is to stop using any registry cleaners and/or optimizers as this is often the result. If you have used any recently and they have a restore function try to reverse what they did.

Go to Start and type cmd in the Search box.

cmd.exe will open in the space above.

Right-click it and select 'Run as Administrator'.

In the Command Prompt window type sfc /scannow (with the space) and click the Enter key and OK any prompts.

Let it proceed as often simply running that will repair the problem. (SFC stands for system file check).

Also don't forget that there are lots of updates still to install following SP2.