Jond is correct. The lasers cannot hurt a cd/dvd - the only issue may be that the some discs may just not play in some players-and this is Not due to damage, but to compatability. For example, some CD-R's (like you burn on your PC) may not play in an old CD player.
Also, the wavelength is shorter (higher frequency) for DVD disks than an Audio CD. This is because there is more information (smaller pits) on a DVD than a CD.
Also, the wavelength is shorter (higher frequency) for DVD disks than an Audio CD. This is because there is more information (smaller pits) on a DVD than a CD.