I just bought my first Apple product, an i-Mac 21.5. I love it except that a loud fan turns on after streaming a movie (netflix) after about an hour. If I simply turn off the computer for 5 minutes the fan turns off and I can resume streaming without the fan. - This has happened repeatedly in the week that I've owned the i-mac. I took it back to my Apple store for a checkup and they told me nothing was wrong. - Is this normal for new i-macs?