What it was: The dominant PC database software from almost the moment it first appeared in 1980, and one of the best-known pieces of productivity software, period; the flagship product of Ashton-Tate back when that company was arguably a better-known name in software than Microsoft.
What happened: dBASE IV, mostly. That 1988 upgrade was late and buggy, and Ashton-Tate didn't move fast enough to fix it, ticking off the loyal developers who had made dBASE a standard. The company also spent a lot of time suing competitors, which is never as productive an investment of time and money as improving one's own products. In 1991, Borland bought Ashton-Tate for $439 million, and acquired dBASE IV's bad luck along with it--neither Borland nor dBASE fared well in subsequent years. And in 1992, Microsoft launched Access, a database that might have slaughtered dBASE no matter what. But dBASE was on the mat before Access ever entered the ring.
Current whereabouts: In 1999, dBASE was sold again, and its new owner, DataBased Intelligence, continues to sell it to this day. (It's now called dBASE Plus, as if dBASE IV had never existed.) The company's newsgroups are surprisingly active, showing that real people are still using dBASE to do real work. Not bad for a product that most of us wrote off as a goner early in the first Clinton administration.
What happened: Hoo boy. Microsoft, after not even bundling a browser with Windows 95 at first, decided to crush Netscape--which it did by bundling Internet Explorer with Windows, giving it away for free, and, eventually, making it pretty good. (Along the way, a certain governmental agency expressed its displeasure with some of the company's anti-Netscape tactics.) Netscape, meanwhile, went off on tangents such as developing a communications suite that didn't amount to much and enterprise software that it eventually sold to Sun. The company sold out to AOL in 1998; AOL had so little interest in the browser it bought that it continued to distribute IE as its primary one. An ever-shrinking user base did continue to get new versions of Netscape, but in December 2007, AOL announced it was pulling the plug.
Current whereabouts: If you're an optimist, you'll focus on one wonderful fact: Firefox, which is based on Mozilla code that originated as an open-source version of Netscape, is a huge success. The Netscape name, however, is profoundly shopworn. In recent years, AOL has slapped it on a budget ISP (which still exists but doesn't seem to be signing up new customers) and an imitation of Digg (now known as Propeller). Today. it's mostly just a slight variant on the AOL.com home page with the Netscape logo repeated endlessly in the background. But did I mention that Firefox is doing great?
What it was: The operating system that powered the original 1981 IBM PC. And then a bunch of clones of the original IBM PC. And then the vast majority of the personal computers on the planet.
What happened: The simplistic answer: When Windows 95, the first version of Windows that didn't require DOS to run, came along, it rendered DOS obsolete. (Eventually--some people happily ran DOS and DOS applications for several years after Win 95 debuted.) More thoughtful answer: The moment that the Mac brought graphical-user interfaces into the mainstream in 1985, it was the beginning of the end of the drab, relentlessly text-based DOS.
Current whereabouts: DOS refuses to die. It seems to me that I still see it in use at small independent businesses such as antique stores and dry cleaners--the kind of outfits that don't bother to change something that still works, even if it's a decade or two out of fashion. It's the inspiration for FreeDOS, an open-source project with a thriving community. And Microsoft still offers MS-DOS 6.22 for download to customers who subscribe to various volume-licensing plans. Why would the company bother if there weren't people who still needed it?