are you having strong exhaust in ur system? as normally optical drives shows problem, as if ur system has faster exhaust at back, and either NO or slower fans at front. this creates a suction inside the casing. then AIr tries getting inside from everywhere. and sometimes passed through the optical drives as well. and the dirt is KILLER.
try cleaning it with CD based clearners, else get it replaced. and not to worry as if this is 5 months old my Sont CD-RW died in just 3 months just because of this suction thingi i told. after that, I keep one front slot open, and as well used a slower and quieter 120MM fan at back.
Intel Core2Quad 2.66Ghz 12MB L2-Cache
4096MB DDR Kingston Hyper-X
XFX 9600GT AlphaDog
Seagate 2 X 320GB SATA2
LG L246WH Flatron 24"