Continuing the spat, in 2001, HP sued EMC for allegedly infringing at least seven HP patents relating to data storage. The HP patents involved data transfers between different storage formats, fail-safe backup storage, server-storage connectivity, and hard drive efficiency boosting.

EMC countersued with at least six infringement claims against HP, for patents involving data mirroring onto different storage systems and other storage technologies.

All along, the business relationship never entirely severed. HP continued to sell VMware, a virtual machine for simultaneously running multiple operating systems. EMC bought VMware last year.

After a jury found HP infringing EMC patents, settlement talks began in February, culminating in a deal yesterday of kiss-and-make-up, where HP shovels $325 million to EMC over the next five years, payment neat or for EMC products. A five-year patent cross-license is also part of the settlement package.

HP shares puffed up 50 cents, or 2.4 percent, to close Monday at $20.97. EMC shares closed down 28 cents at $12.84. That message: HP closed a open liability, while EMC's open-ended upside closed.

All sides professed satisfaction, including the patent attorneys representing both firms, their coffers bulging, making this a patent story with a happy ending all the way around, as well a cautionary tale for trigger-happy patent holders to pick their targets carefully.