Although some might say that optical media is pretty much doomed and that digital downloads are about to take over the world, the truth of the matter is that CD-ROMs and DVD-ROMs remain the favorite content delivery “vessels” for a wide array of content types, whether we're talking about software or entertainment. However, since both types of units are based on a laser (optical) reading system, they tend to get dirty, especially when the computer or standalone player they're a part of is installed in a very dusty environment.
So, if you're beginning to experience various problems when inserting discs into the CD-ROM or DVD-ROM units, then perhaps it's a very good idea to clean the lens. Of course, before going ahead and doing anything to the reading unit itself, you should first check the disc in whose case the issue manifested. If the disc is OK or if the same problem occurs in the case of other discs as well, then you'll most likely have to clean the inside of the optical disc.
The easiest method to remove dust from the lens is to blow it away with a jet of air. However, be advised, the respective jet of air shouldn't really come from your own mouth, since it would be accompanied by all sorts of micro-particles and saliva. Instead, you should try another device that produces strong jets of air, such as the air bulb used by photographers for cleaning lenses or even a can of compressed air (although the latter solution is not particularly recommended, unless you have a really steady hand).
If you've got the air bulb, than all you have to do is open the device's tray and blow evenly across the entire length of the tray's slot, in both directions. In this way, you'll ensure the fact that there's absolutely no dust left.
However, if you're using compressed air, you should be very careful about the pressure at which air is blown out of the tube. Thus, you should press quite gently on the button, and also maintain the gas can in vertical position. Otherwise, the liquid gas at high pressure found within these tubes might actually wind up on the CD/DVD-ROM's lens, and that's the last thing you want to do.
]Nevertheless, for some users, simply blowing the dust off the lens is not enough, and in that case, you should get ready to pull out the heavy artillery, namely a CD cleaning disc. These discs can be found in just about any music store or specialized computer store, and work equally well on both CDs and DVDs (after all, the construction of the lens is almost similar in both product variants).