When it starts playing, hit CTRL-ALT-DEL and see if you can spot any running processes you don't recognize in the Task Manager. Also, go to Start > Run and type msconfig, and click the Startup tab. Look and see what things you are loading on startup that might be the culprit. You can uncheck anything you find that looks out of place, and then click OK. Restart your computer and see if the problem has gone away. if it has, you can run msconfig again and re-check each item one by one, restarting after each one, until you find the one that caused the problem. Also try running a spyware checker such as Lavasoft's Adaware, or Spybot Search & Destroy, since the problem may be related to malware on your system.