Up until the time that Microsoft introduced Windows XP, you could purchase a program and install it on more than one computer. Though this wasnt necessarily true with operating systems such as DOS or Windows, they were sold for use on a single computer, other software used a like a book license agreement. It essentially stated that you could install the program on more than one computer as long as only one person was using it at any given time. Since no two people can read the same book at the same time, the like a book phrase was used. Some programs were sold that allowed you to install them on more than one computer by use of an install/uninstall routine that added to and subtracted from a file on the floppy disk. Lotus 123 was sold this way, you had to remember to uninstall the program if you defragged the disk, or you would have to use one of the remaining install routines. When you used them all up, you had to contact the company and purchase another license diskette. Nowadays, most programs will only allow you to install them on a single computer. Some programs do allow you to install them on the office computer and a laptop or home computer, while others are strictly a single-user license. What the software companies have moved to is a procedure named product activation. When you install the software, you must enter in an installation key number that is included with the CD. The installation program will take this number and give you a second key. You are then required to go online or to call a number to complete the installation. The number that is included with the program is a unique numberno one else will have it. The second number, the one that the computer generates, should be unique to your computer. This number is based on the number from the CD along with a number that is derived from your computers configuration. The installation program takes the serial number from the CPU, the amount of memory, network card make, hard drive make and size, along with a number of other values from other devices in your system, to generate this second number. When you supply these two numbers either online or over the phone, you are supplied with a third number that you have to enter into the program to complete the installation. Once this is done, the software company will not allow the original number from the CD to be used again, so you cant install the program on another computer. The activation program will usually allow you to add more memory, upgrade the hard drive, and make other changes to the computer. As long as certain key items remain unchanged, the program will allow the changes and the program will continue to run. If it determines that there have been significant changes that it may be on a different computer, it may require you to re-activate the product either online or by calling customer service. Richard Heller is an independent computer specialist who specializes in repairs, installation, upgrades, technical support, Internet sharing, data recovery and diagnostics. If you have any computer or service-related questions, please send them to The Rock River Times, e-mail email@example.com, or call 243-1162.