As many people have and will have cd/dvd combo drives at least for a while into the future I thought it might be pertinent to mention that combo drives contain two lasers. One for the CD-rom operations and one for the DVD operations. Apparently aside from the fact that dirt/dust/etc can build up and it might help to clean the lens.
I had been reading some about a stated issue where the cd-rom laser is not engaging quite to the height that it should and that fixing it involves using a multi-meter and minute(sp? mine-nute) changes. I have not read enough to properly understand, try and report on this at this time though.
What really stinks is the fact that if my cd-rom/dvd drive is just dirty and thus having issues with the cd-rom portion it is a real pain as I have a lens cleaner disc however it is a cd-rom disc and therefore the drive only engages for a few seconds for which I doubt it has done any good
It's too bad that there are not programs to tell people how well the laser is reading a disc and one could know about the impending dirt buildup or failure of a cd-rom/dvd drive.