Cause of death: proprietary hardware
This was an early attempt at running both data and voice over the same phone line, way before VOIP became a reality. You used a matched pair of these modem-like devices at either end of a phone call, which was the major problem, because the protocol was proprietary. The company was sold to SystemSoft in 1995 and its technology was integrated into their higher-end call control products.
Cause of death: corporate malfeasance
Before there was Linux there was Unix and the company that brought Unix to more desktops than anyone else was SCO. Prior to SCO, the major Unix vendors were either AT&T or minicomputer hardware vendors. The first versions were quirky affairs and required lots of care and feeding, but once they were setup they ran forever. SCO sold the rights to Unix in 2001 to Caldera Systems, a company that was founded by Ray Noorda, who made his fortune with Novell, and that began a protracted legal battle with just about everyone else in the Unix universe.
Cause of death: Lotus 1-2-3
The first big application for PCs was VisiCalc spreadsheet software, developed by Dan Bricklin and Bob Frankston. I remember running it on an early HP -85 computer that is pictured above with a small screen and printer along with a tape cassette for its memory. VisiCalc was never patented (at the time there was no such thing as software patents) and subsequent versions, including Lotus' 1-2-3, improved upon the spreadsheet and made them popular.
Cause of death: Ashton-Tate and later Borland
In 1984, the most popular word processing program was called Multimate, and it was used largely because it mimicked the user commands of dedicated Wang word processor machinery. In those early days, a software vendor would have to produce different versions specifically for each PC OEM. But its popularity would prove its undoing, making it an attractive take over target for database vendor Ashton-Tate. Eventually, when Tate was sold to Borland the product disappeared.
Cause of death: faster and cheaper Ethernet
Thomas Conrad was one of the more popular vendors of one of the early 1980s networking standards called Arcnet. It had the advantage of running over cable TV coax. And like many of the networking adapters of that era, there were hardware switches you had to set (see the picture above) to configure it properly before you installed it in the PC. It was a cheaper alternative to the token ring cabling from IBM and Ethernet. It was the predecessor to 10BaseT topologies that are in vogue today. Many of the early Novell networks ran on Thomas Conrad Arcnet equipment. But as Ethernet became more capable and faster with 100BaseT, the topology died out.
Cause of death: Microsoft, integration into the operating system
When hard disks were 20 megabytes, storage was at a premium and a small company in southern California came out with special software that could double your storage space. Stac lasted until 2002, and was the victim of Microsoft tactics to include a similar feature in MS DOS v 6.0. Even though they won a $120 million lawsuit, the company never recovered, as hard drives got bigger and cheaper quicker. Eventually, the intellectual property was purchased by Altiris, who is now owned by Symantec. And most operating systems now include their own disk compression, thanks to early work by Stac.