Whrrrrrrrrrrrrrrrrrl! Whrrrrrrrrrrrrrrrl! That's the sound of a fan running loud, and if you are in a particularly unlucky situation, it'll be quickly followed by the computer shutting itself off. Or sometimes it will be accompanied by a searing hot bottom side of a laptop. Other times, the laptop is super hot, but no sounds of fans can be heard. What does it all mean?

Experts say that chances are the loud fan is a sign of a failing fan. "Most fans, when failing, grow very noisy first. That is generally due to the bearings in the fan. Additionally, if you start to notice lockups, blue screens, or problems that seem to occur more frequently the longer your computer has been on, the quick solution is to open the side panel of the computer and make sure the fans are spinning," says Brett Jaffe, president of IT4, a Boston-based IT company.

If you find a failing fan, getting it replaced is important as a functioning fan is essential to a well-running machine. Replacement fans can be purchased from computer supply stores or online at sites like eBay. Just be sure you know what fan you are placing and the make and model of the computer you are installing it in. "There is generally a fan on the power supply (which you can feel from the rear of the supply), a fan on the processor (though sometimes just a heat sink), and sometimes a fan on the video card. Many computer cases may have additional fans for cooling. A cool computer is a happy computer as heat is the number one killer of computer components (actually, dust seems to be the main cause since it cases more heat and can be a source of a failing fan)," says Jaffe.

However, if your computer is running hot and all the fans are functioning, you might just be a victim of a hot-running processor. "The sound alerts you to dust, clogs, and mechanical failures. But some processors do run hot -- Pentium 4s, for example," says Ryan Meyer, president of Meyer Technology Group.

Another good idea to ensure your computer runs cool and safe? Download a program to help you monitor it. "There are a variety of free tools one can download to monitor fans and temperatures such as Notebook Hardware Control (http://www.pbus-167.com/), SpeedFan (http://www.almico.com/speedfan.php), and more specific tools from Intel and OEMs such as Dell and HP," says Meyer.

Preventative maitenance is key when you're running a business.  Don't hesitate to replace a noisy fan - especially since an overheating computer can risk data loss!  Its better to quickly remedy an initial problem than let it fester and cause damage to the rest of the machine.