with regards to keyboard you may have accidently activated something called sticky keys , many years ago before games macros were invented you had to hold your finger on a key for a long time or tap it very fast. google sticky keys at top of screen a big box will appear telling you how to turn them on off.
Finally do you have problems with anything else that gets plugged into the same usb sockets , you may find flash drive cant work properly if a socket is faulty. you can check the microphone in sound settings , if you get a loud buzz it could either be the sensitivity of you microphone is set too high , it could also be a faulty or worn usb socket , jack plus give a buzz if they begin to wear. To cut down on wear of pc's usb sockets I plug my headset into a short usb extension.
if you hve any of the half life games they have a microphone gain set up in them. As I say buzzing is sometimes caused by the mics controls set too high.