HDD constant access noise driving me crazy

I've had my Dell XPS 720 for 7 months now and the constant hard drive noise is driving me insane. No matter what I'm doing, idle or not, it is always writing to the hard drive and the constant noise is maddening. I've just disabled Windows defender, Superfetch and Windows search indexing and it has gone silent whilst I write this, but this is not an ideal solution. Can I minimise how often these services access the hard drive? It's a pain to switch them all off every time I want to watch a movie or listen to music.

I'm running Vista, 2.4Ghz Intel Quatro 6600, 3GB Ram, 921 GB HDD

 

This sound like a faulty HD problem it should still be under guarantee. I would backup any critical data and have it replaced it should not be making a noise.