Apple did not lose the PC market to Microsoft.

Apple is a computer maker.

Microsoft is a software company.

Apple also makes software, for its own computers. But it's primarily a maker of computers. Microsoft isn't.

This so often repeated myth compares apples to oranges, pun intended, and is as a result meaningless.

When you compare Apple as a computer maker to other computer makers, then the story changes. Its percentage of the market is heavily competitive with other companies who make computers.

If Apple were a software company, vying with Microsoft to become the biggest software vendor, then this would make sense. However, Apple was a computer maker, one that created software for its own computers. Apple would have loved to get everyone in the world using their computers instead of PCs, sure. Yes, part of the reason that didn't happen is the way that Microsoft would run on any PCs. However this is partly because Microsoft didn't MAKE any PCs.

Again, it's simply a false equivilance but it's tossed out all the time and no one notices.