Imagine a world in which Microsoft wasn't allowed to sell Windows or Word, no one could use a Blackberry, Intel's chips were taken off the \n\nmarket and every company that wanted to deploy Linux had to pay an exorbitant fee to an obscure software vendor.That world doesn't exist, of course. But each of those scenarios could have been realized if the outcome of five major patent lawsuits had been \n\ndifferent. It easy to dismiss the recent lawsuit by Apple against HTC, the maker of Google's Nexus One smartphone, as something that only lawyers need to care about. Indeed, most \n\nlandmark patent suits are settled \u2014 often at great expense \u2014 without causing an upheaval in the technology industry.Even so, patent litigation has become more than a cottage industry in Silicon Valley. On the one hand, it protects intellectual property developed by \n\nindependent entrepreneurs and industry giants alike. But it also wastes untold millions of dollars a year that could be better spent on innovation, says \n\nCharlene Morrow, who heads the patent litigation practice of Fenwick & West. "When startup valuations were very high, and a new company got a \n\nround of funding, you could absolutely count on a non-practicing entity to file a patent suit," she says. Non-practicing entity? That's a polite term for what others call a "patent troll," a company that purchases a patent, often from a bankrupt firm, and \n\nthen sues another company by claiming that one of its products infringes on the purchased patent. Patent trolls typically have no actual technology or \n\nproducts on the market. We've tapped the memory banks of Silicon Valley veterans who recount five of the most sensational patent cases ever to roil the technology \n\nindustry. 1. Who invented the GUI?Although it seems like a relic of the distant past, it's only been 30 years since Microsoft launched Windows 3.0, its first successful operating system \n\nto sport a graphical user interface. It was a great idea, but whose idea was it anyway? According to Apple founder Steve Jobs, it wasn't Microsoft's; it was Apple's. Or was it? Legend has it that Jobs actually got the idea when he took \n\na tour of the famed Xerox PARC and saw an early version of a windowed operating system, recalls long-time semiconductor analyst Nathan \n\nBrookwood of Insight 64. Whether that's true or not, Apple claimed that the "look and feel" of the Macintosh operating system, taken as a whole, was protected by copyright, \n\nand it sued Microsoft in federal court in 1988. Not to be outdone, Xerox jumped into the fray before the original action was resolved and sued Apple \n\nfor stealing its ideas. After six years of litigation and appeals that went all the up to the United States Supreme Court, both suits were dismissed; Apple's because it \n\ncouldn't prove its claims, Xerox's because it had waited too long. 2. Is it Linux or UNIX?In early 2003, an obscure software company called SCO, which had come into existence via a Byzantine series of mergers and technology sales, \n\nshocked Silicon Valley by announcing that part of its UNIX system code had found its way into Linux. SCO, which hadn't invented the code, refused to \n\nidentify the specific segments of the software, claiming that it was a secret which they would reveal only to the court.A flurry of lawsuits followed, including a $1 billion action against IBM, and suits against Novell, Red Hat and Daimler Chrysler. For a while, there \n\nwas fear that third party customers who used Linux could be liable for huge damages to SCO. There were allegations that Microsoft, in a truly \n\nMachiavellian move, had funneled money to SCO to help fund a lawsuit that would damage its competitors. Ultimately, though, the cases fell apart. 3. No Crackberry for youHardly anyone had heard of a tiny Virginia-based company called NTP. That changed in a hurry when NTP, which held a basketful of wireless \n\npatents, brought suit against RIM, the inventor of the wildly popular Blackberry. A jury agreed that the patents were valid and RIM was hit for $53 \n\nmillion in damages. Had it ended there, it would have been just another expensive lawsuit. But a judge then ruled that RIM was continuing to violate NTP's patents by \n\noperating the Blackberry data network. He could have issued an injunction to shut down the service. Panic ensued as everyone from Wall Street traders \n\nto senior advisers at the White House faced the loss of their favorite electronic gadget. Ultimately RIM settled for $615 million, one of the largest ever settlements in a technology patent case. The NTP suit sparked outrage in many quarters at the perceived unfairness of the patent system. However, in a more recent patent case known as \n\neBay vs. MercExchange, the U.S. Supreme Court issued a ruling making it less likely that a patent holder could win an injunction to shut down the \n\nbusiness of a patent violator, says Michael Sacksteder, a patent attorney with Fenwick & West.4. Chips AhoyIntel and a workstation maker called Integraph tangled in a complex series of patent lawsuits beginning in 1997. Integraph claimed that Intel, the \n\nworld's larger microprocessor maker, had stolen key features of its Clipper chip. One settlement, which that involved memory design, cost Intel about \n\n$300 million. A second alleged infringement involving a microprocessor instruction set known as VLIW was settled for $225 million. Brookwood notes \n\nthat the settlement was more money than anyone ever made bringing that technology to market. At $525 million, the Integraph litigation resulted in the \n\nlargest set of damages ever won against Intel. Making matters even more complicated, computer makers, including Hewlett-Packard, became involved because they had purchased chips from \n\nIntel that included memory features claimed by Intergraph. Ultimately, those claims were settled as well. 5. A Gold Medal for the CanadiansIt would be hard to find a product that has a larger user base than Microsoft Word, or an application that makes more money for its inventors. So \n\nwhen a tiny Canadian company called i4i won an injunction preventing Microsoft \n\nfrom selling Word, the world noticed. The 30-employee company claimed that Microsoft had infringed on a patent for the use of an XML feature. Microsoft never stopped selling Word, \n\nbut it has removed the featured from Word 2007 and the upcoming Office 2010 and paid $290 million in damages. It's worth noting that i4i filed its case in the small East Texas town of Tyler, a venue considered the friendliest in the United States for claims brought \n\nby patent trolls.One other bit of tech patent history: It appears that the term patent troll was first used by Chuck Mulloy, a veteran tech industry public relations man \n\nwho has fought on both sides of the Intel-AMD chip wars. As Mulloy recounts, Intel was defending a patent case brought against it by a company called \n\nTechSearch. In an interview with reporter Dean Takahashi of the Wall Street Journal, the normally affable Mulloy let his irritation show and he referred \n\nto TechSearch as a "patent extortionist."TechSearch's lawyers quickly added a libel case to their suit. After a huddle with corporate attorneys, Mulloy retracted "patent extortionist," and \n\nsubstituted the milder "patent troll." "It's like the troll that lives under the bridge, but doesn't own it, and charges a toll on everyone who crosses," he said \n\nrecently. San Francisco journalist Bill Snyder writes frequently about business and technology. He welcomes your comments and suggestions. Reach \n\nhim at firstname.lastname@example.org.Follow everything from CIO.com on Twitter @CIOonline.