That sound is definitely your fan and is caused by dust. Happens to me about every eight or nine months. My home doesn't have a forced air heating and cooling system so there isn't any flow of air through a filter. As a result, we get dust build up on everything. The inside of my case has to be cleaned out every six months or so. If I forget to clean it out, the fans get clogged up and make a bunch of noise.
Most cooling fans have bearings which will make noise when they get too dirty. Simply using an air duster every year or so will really help your system. Not only does the dust slow your fans and make them noisy, which reduces their cooling ability; the dust settles on other components which acts like a blanket that traps the heat inside making your system run hotter.
Most processors and other PC components work better when they are at room temperature. If your system gets hot, then your performance with be affected. You may notice a slow down or frequent and seemingly random errors.
You should unplug your system and wait about 2 minutes and open your case. You systems capacitors will hold electricity for a bit which is why you should wait. Be sure to remove any static charge you may have by touching something metal other than you computer before touching ANYTHING inside your computer. An anti-static wristband is always a good idea.
Using an air duster (use 2 or 3 since they freeze up quickly) blow out ALL dust in your system. Don't just blow it around inside the case, really get it out of the system. Some people use a vacuum cleaner to clean the dust out. I don't recommend this practice since spinning air is flowing over a plastic tube which is a great way to generate a lot of static electricity. Use a clean (preferably unused) paintbrush to lightly brush off any stubborn dirt and dust. Also, using the paintbrush can help get the dust that settles in the bottom of the case after your air dusting. Be sure to blow the air duster through both sides of any fans you have. This will help get ALL of the dust out of them. One additional thing to remember when cleaning out your case is that most power supplies have their own fan and because they get pretty hot, tend to trap a lot of dust inside. You may need to open your power supply and clean it out too.
There are things that you can do to prevent the build-up of dust in your system. First, never smoke around your system. Smoke is sticky and doesn't simply pass through your system without issue. Smoke sticks to your components and then the dust sticks to the smoke, etc, etc, etc...
Using a filter on ALL incoming are fans and vents will trap the dust before it gets into your system. This is easier in some systems than others. If your system has a bunch of vent holes in it, you may have to wrap the entire case with filter material. Be sure to not cover any outgoing fans or vents. You don't want to trap the dust inside. Be sure that you have plenty of outgoing air fans and vents. If all of your fans are inbound then your system will have a positive pressure cooling system which is great for keeping out dust if ALL of your incoming ports are very well filtered. If they are not filtered properly, then MORE dust is trapped in a positive pressure cooling system. Alternatively, having a negative pressure system will actually suck dust into every opening in the case like a vacuum cleaner core. This is when you have to consider wrapping the entire system with filter material.
Ideally, you should have a neutral pressure cooling system where as much air is forced into the system as is forced out. For example, you may want two fans in the front blowing cool air in and two fans in the rear blowing hot air out. That would maintain proper air flow and few dead air pockets in the case where dust would settle.
Filter material is pretty easy to find. Using a universal window air conditioner foam filter is the most common method. Filter material can also be cut from heating and cooling filters. These are the 1 by 20 by 20 inch (2.54 X 50.8 X 50.8 cm) or similar sized filters. Placing a fabric softener sheet over an outgoing fan port will have your office or computer room smelling like a laundromat.
If dust is really bad, look into buying a sealed, positive pressure, filtered computer case. These are more expensive but run very cool and trap nearly all of the dust before it enters the system.
Hope This Helps.
vujsa
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) and looking at the fans to see if they can spin freely and that nothing is blocking them. All 4 of them were clear and could spin freely.