Backward Compatibility of XP

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When designing Windows XP, Microsoft wanted to make it easy to implement the new operating system without having to rip out and replace earlier elements or embark upon extensive customization. The company invested significant research and development dollars to address reasons why applications would run on older down-level platforms but not on later ones. Microsoft's developers found, for example, that many applications were hardcoded to look for a particular operating system version. If the program checked the registry or memory and did not find the release it expected, it simply would not run. To get around this, XP developers programmed XP to "lie" if an application insisted on, say, Windows 9x, so the program would run without problem. This improvement translates into potentially significant cost savings, as an agency can leverage its current applications while also gaining the added features of the latest operating system. As a result of this feature, some organizations have chosen to bypass Windows 2000 and move desktops directly to XP. That way, they could run more of their existing applications on Windows XP than on Windows 2000 without having to write customized middleware.

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