Microphones doesn't work help please

Hello,
i need to some one help me with me mic doesn't work any of my Recording devices I have logitech web cam with a mic it was working fine for long time till I uninstall it and try to reinstall It won work anymore just my Microphones. recording device. they look just all work fine but they're not working I got a windows] vista. and my xp my web cam and mic works perfect