It can also be cheap Hardware, motors and transformers microphones etc bad Earth

In the old days you were advised to ensure only one earth connection should be made to amplifiers etc. Not sure if this is possible with the built in cables these days.

You need one of these, it's an earth loop eliminator. All it is, is a 1:1 transformer, I used to make them back in the days when you couldn't buy them commercially, it is a standard trick audio engineers use, much safer than starting to lift the safety earth on electrical equipment which is quite a dangerous practice, many a good artist has been electrocuted because their guitar was not earthed ;)

You could get an exteral sound card for a fiver or less on amazon no bigger than a memeory stick, that would make your mic usb that might help .Also check all your settings as there are TWO mic selections in windows and you only need the one on the mixer to be selected check if the other one is muted or not mines is best muted