I understand that since updating your HP TouchSmart IQ500.it Desktop PC to Windows 8.1 your microphone is not working. This is probably due to the fact that as there are no Windows 8.1 drivers listed for your computer on the HP TouchSmart IQ500.it Desktop PC Drivers page you must me using Windows generic drivers. As the drivers you are using are not specifically designed for your hardware there may be some loose of functionality. I suspect that your audio input is not supported under Windows 8.1 and that is why it is not working.
The only way of knowing for sure would be to recover back to factory and see if the microphone works again if it does you know you will not be able to use your microphone under Windows 8.1 unless you upgrade your hardware.
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Dunidar I work on behalf of HP
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