Overview of Common Application Compatibility Issues

           An application written for a specific operating system can cause problems for several reasons when you install it on a computer with a different operating system. Generally, applications and hardware that work on Windows 7 will continue to work on Windows 8.1. To troubleshoot and address any compatibility issues effectively, it is important to be aware of the general areas that typically cause the most issues.

Setup and Installation of Applications: During application setup and installation, an app might try to copy files and shortcuts to folders that existed in a previous Windows operating system, but no longer exist in Windows 8.1. This can prevent the app from installing properly or even installing at all.

UAC: User Account Control (UAC) adds security to the Windows operating system by controlling administrator level access to a computer and by restricting most users to run as standard users. When users attempt to launch an app that requires administrative permissions, the system prompts them to confirm their consent to do so.

WRP: Windows Resource Protection (WRP) protects Windows resources such as files, folders, and registry keys in a read-only state. This affects specific files, folders, and registry keys only. WRP limits updates to protected resources to the trusted operating system installers, such as Windows Servicing. This enables better protection for components and apps that ship with the operating system from the impact of other apps and administrators. However, WRP might cause the following compatibility issues:

• Application installers that attempt to replace, modify, or delete operating system files or registry keys that WRP protects might fail with an error message that indicates that the resource cannot be updated. This is because access to these resources is denied.
• Applications that attempt to write new registry keys or values to protected registry keys might fail with an error message that indicates that the change failed because access was denied.
• Applications that attempt to write to protected resources might fail if they rely on registry keys or values.64-Bit Architecture: All Windows 8.1 editions are available as 32-bit and 64-bit versions. The 64-bit version of Windows 8.1 can run all 32-bit apps with the help of the Windows 32-bit on Windows 64-bit subsystem. Considerations for the 64-bit Windows 8.1 include:

• Apps or components that use 16-bit executable files, 16-bit installers, or 32-bit kernel drivers will fail to start or will function improperly on a 64-bit version of Windows 8.1.
• Installation of 32-bit kernel drivers will fail on the 64-bit system. If an installer manually adds a driver by editing the registry, the system will not load this driver, and this can cause a system failure.
• Installation of 64-bit unsigned drivers will fail on the 64-bit system. If an installer manually adds a driver by editing the registry, the system will not load the driver during load time if it is not signed

WFP: Windows Filtering Platform (WFP): is an application programming interface (API) that enables developers to create code that interacts with the filtering that occurs at several layers in the networking stack and throughout the operating system. If you are using a previous version of this API in your environment, you might experience failures when running security-class apps, such as network scanning, antivirus programs, or firewall apps.

Operating System Version Changes: The operating system version number changes with each operating system release. For Windows 7, the internal version number is 6.1; for Windows 8, the internal version is 6.2; for Windows 8.1, the internal version is 6.3. The GetVersion function returns this value when it is queried by an app. This change affects any app or application installer that specifically checks for the operating system version, and this change might prevent the installation from occurring or the app from running.

Kernel-Mode Drivers: Kernel-mode drivers must support the Windows 8.1 operating system or be redesigned to follow the User-Mode Driver Framework (UMDF). UMDF is a device driver development platform that the Windows operating system uses.