I've seen dusty PC's, but, that CDROM Drive is definitely bad. Looks like there isn't a good intake and the air is all entering the case through the drive.
At least the dust LOOKS grey. IMHO, the worst is working on a PC from a heavy smokers household. The dust is yellow and tacky... and just "BLECH"! It's amazing how smoke will 'yellow' pc parts. Seeing that it's amazing people would allow it in their lungs!