WinZip is entirely trustworthy software. (However, if you're actually looking for file compression software, 7-Zip is just as good and it's free:
http://www.7-zip.org )
With regard to your sound problem, start by checking for anything physical. i.e. if you're using external speakers check that they're properly plugged in. Also check that the volume control on them isn't a bit scratchy. Try using headphones to see if the problem is related to just your speakers or to all sound output.
Then try sounds from a different source (e.g. play a CD or MP3 file with your media player). If the problem only relates to Youtube, try a different browser (or reset your main one). If the problem is present with all sound sources (and doesn't seem to have a physical cause), reinstall your sound driver.