Some MP3 files sound glitchy

There are two possible reasons for this. First is a bad MP3- this is possible. If it glitches in every player, then it may be a bad recording or encode. You should simply download a better copy.
The second reason is your computer is using the wrong audio codec. This is quite common, since some codec packs will interfere with the settings. To correct this:

• Go to Control Panel > Multimedia > Devices
• Expand Audio Compression Codecs
• Double click on the Fraunhoffer IIS MPEG layer 3 Codec
• Make sure it is enabled, and set it's priority to 1