I have a PIII full tower I built in 1999 and smoked like a champ in front of for 10 years. (cleaned it out about every 2 years) It still runs tickety-boo. But then, I built it, not Apple. Major difference. Every component built by a manufacturer that specialises in that type of component and provides a 3 year manufacturers warranty. I've never had to make a warranty claim on gear purchased by this rationale.
Apple: masters of the unmountable floppy. (thus the floppyless iMac)
Where's my iIt post? Just about time to drag it out again...