should I worry?

I have a Dell laptop ( less than a year old) running win 7. I have heard a noise this morning which sound lake a fan ( faint screech), so I immediatly closed the lid. Do I need to worry about this? I have yet to produce the noise again.

Sounds like the fan is failing. As they get worn, they occasionally become unbalanced when spinning, creating that screeching noise, or a rubbing/knocking noise. The noise will get more and more frequent from now on. I shouldn't worry about it until it becomes either an annoyance, or the temps start going up.

You should be able to get a replacement from the supplier, or you can search for your laptops model number + 'replacement fan' and you should be able to find one, but they are expensive. I once paid £20 for a replacement fan on my tablet. The fan was free, but I had to get if from Taiwan and they wanted money to ship it. Then the bank charged me another £20 for the wire transfer.