IF you’re the owner of a Windows PC who is looking for a replacement computer, the choices are grim. You can step into the world of hurt that is Vista, the latest version of Microsoft Windows that was released in January. Or you can seek out a new machine that still comes loaded with the comparatively ancient Windows XP.

Maybe, you might say, the moment has arrived to take a look at the Mac. You can easily order one online, of course. But if you’d like to take a test-drive before you commit, odds are that you’ll have to look far and wide for a store that sells it. The Mac’s presence in the retail world remains limited, a shame given the rare opportunity for Apple to gain market share that opened up when Vista arrived.

The Mac’s worldwide market share was 3 percent as of June 2007, according to Roger L. Kay, president of Endpoint Technologies Associates, a consulting firm in Wayland, Mass. That forlorn number looks even worse compared with Apple’s peak worldwide share of 14 percent in 1984, the year the Macintosh was introduced and sales of Apple II computers were the company’s mainstay.

Mr. Kay noted that Apple’s share was as low as 2 percent as recently as early 2004. He said the increase to 3 percent may be a result of the “halo effect” produced by the success of the iPod. It could also just as easily be attributed to Apple’s simply offering better products at more competitive prices, he added.