Why Applications Fail

The following list describes common compatibility issues for Windows 7, particularly when using an application originally designed for Windows XP:

• User Account Control In Windows 7, by default, all interactive users, including members of the Administrators group, run as standard users. User Account Control (UAC) is the mechanism through which users can elevate applications to full administrator privileges. Because of UAC, applications that require administrator rights or check for administrator privileges behave differently in Windows 7, even when run by a user as administrator.
• Windows Resource Protection Windows Resource Protection (WRP) is designed to protect the system in a read-only state to increase system stability, predictability, and reliability. This will affect specific files, folders, and registry keys. Updates to protected resources are restricted to the operating-system trusted installers (TrustedInstaller group), such as Windows Servicing. This helps to protect features and applications that ship with the operating system from any impact of other applications and administrators. This impact can be an issue for custom installations not detected as set up by Windows 7 when applications try to replace WRP files and registry settings and check for specific versions and values.
• Internet Explorer Protected Mode In Windows 7, Windows Internet Explorer 8 processes run in IEPM with greatly restricted privileges to help protect users from attack. Internet Explorer Protected Mode (IEPM) significantly reduces the ability of an attack to write, alter, or destroy data on the user's computer, or to install malicious code. This could affect ActiveX controls and other script code that try to modify higherintegrity- level objects.
• Operating system and Internet Explorer versioning Many applications check the version of the operating system and behave differently or fail to run when an unexpected version number is detected. You can resolve this issue by setting appropriate compatibility modes or applying versioning shims (application-compatibility fixes).
• New folder locations User folders, My Documents folders, and folders with localization have changed since Windows XP. Applications with hard-coded paths may fail. You can mitigate this by using directory junctions or by replacing hard-coded paths with appropriate API calls to get folder locations.
• Session 0 isolation Running services and user applications together in Session 0 poses a security risk because these services run at an elevated privilege level and therefore are targets for malicious agents looking for a means to elevate their own privilege level. In earlier versions of the Windows operating system, services and applications run in the same session as the first user who logs on to the console (Session 0). To help protect against malicious agents in Windows 7, Session 0 has been isolated from other sessions. This could impact services that communicate with applications using window messages.