I'm a PC, and I run Linux.
What's a PC? PC is an abbreviation for Personal Computer. A PC is a personal computer.
Technically speaking, the Macintosh is also a PC. It's an Apple architecture PC with an Intel or PowerPC processor. Microsoft operating systems run on IBM architecture PCs with Intel or AMD processors.
Linux runs on Apple and IBM architecture PCs, and is free.
So when you see Apple's and Microsoft's propagandavertisements, what they're really trying to prove is which operating system is better - not whether an Apple or IBM PC architecture is better.