-Does your CPU cooler look like this?
-If it does, then it DOES need cleaning. As you can see, a dusty film covers the passive cooler, and thus disables the air-flow through it. That results in increasing of the temperature, instead of cooling.
-How can you detect this, without opening your PC case? Simply, a PC with a dusty cooler like this one, usually works very unstable, turns off by itself, and can refuse to be turned on (for 15 to 30 minutes, until the CPU cool down a bit). If this "dust film" isn't removed soon, the electro-lit condensers around the CPU get dry, and in time the motherboard can become unusable. So, solve the problem as soon as possible, or it might cost you expensive.
-How to solve the problem?
-At first, check if the PC is under warranty. If it is, then just contact the seller. They should tell you what should be done further. If not, read on :-)
Take what you need:
1 x vacuum cleaner
1 x brush (not too small, but not too big. A paint brush may do the job.)
1 x screwdriver (possibly, some PCs have tool-less opening design)
Unplug the PC, and place it in the middle of a clean desktop, or on the floor. Plug the vacuum cleaner, and turn it on, at middle vacuuming). Using the brush, carefully get rid of the dust while cleaning the dust with the vacuum. Do the process until the "dust-film" is completely removed. This way you can clean the whole inside of the PC, but be very careful. The vacuum cleaners a always hungry for electronic components, so don't get them too close to them :-)
Close the PC case, and connect it back, as before.
Warnings:
-Do not get too close with the vacuum cleaner to the electronic components. A strong vacuum cleaner easily may take them off their place :-)
-Do not play with the vacuum cleaner and the active cooler. It sure buzzes in an interesting way, but it bay break it.
-Be gentle with the brush, it can easily damage the components.
Legal notice: I, in no way take responsibility for any damage that can be caused, either to the PC, or you. If you are not sure what you are doing, leave this job to a trained professional.
