Re: CDs/DVDs

Wash them in soapy water and dry with a soft cloth

Re: CDs/DVDs

Because the disc is read similar to a record (though from the centre out). If you accidentally scratch the disc following the track direction a large area of data could be affected which is uncorrectable. If you scratch it accidentally at right angles to the track only a small piece of data will be affected and the CD checksum correction will kick in. (Remember how CDs were originally touted to be almost impossible to damage?)

In actual fact the easiest way to damage a CD or DVD is by writing on the label side because the data is just below the label with only a thin layer of protection whereas on the 'reading' side it is protected by a thicker layer of plastic.