First of all, welcome to BC. See, it's a great site, your problem has gone away already !
On a more serious note, what sort of noise is it ? Sort of a fan whirring noise, or is there an element of click to it ? There are three things I would do as a precaution / check.
First off, back up my data - work, photos, music, that sort of stuff. Depending on how much you have, you can use anything from a USB stick to an external USB hard drive. But back it up, just in case you do have a hard drive problem.
Secondly, run chkdsk /r on you hard drive. You do this by opening the Command prompt which you will find at 'Start / Programs / Accessories'. RIGHT click on 'Command prompt' and select 'Run as administrator' in the drop-down box that appears. This will produce a black window with white text. Just type 'chkdsk /r' (Note - there is a space between 'chkdsk' and '/r') and press enter. You will then get a message saying it cannot run, do you wish to run at next boot Y / N. Type 'Y' (= Yes) and press enter, then reboot your computer. Chkdsk will run when it starts up.
Dependiing on the size of your hard drive and the speed of your processor, this may well take upwards of an hour, don't turn your computer off until it has finished. It will then tell you if there are any faulty sectors on your hard drive.
Thirdly I would download, install and run a little program called 'Speccy', you can get it here :
The noise may be nothing to do with your hard drive. You say your computer is four years old, you will be surprised how much dust and dirt can accumulate in that time and this will make the fan work much harder to keep temperatures down. Speccy will tell you far more than you want to know about the hardware on your computer - but it will tell you some important temperatures. On a laptop, the CPU should not exceed about 50 - 60C, the motherboard should be around 30 - 40C, as should the hard drive. These temperatures are after it has been in use for about an hour or so.
If anything seems out of line, or you just want somebody to have a look at it, it is very easy to generate a report from Speccy. The method is that the report itself is stored on their server and you get a link which you can paste into a post here. There is no personal data included in the report. And if chkdsk shows up any errors on the hard drive, post back as well for more advice.