In Windows 10/8/7/Vista, when you installs an older version software or program which is not compatible to work with the latest version of Windows, A Program Compatibility Assistant will appear to warn you about the incompatibility of program and shows you options to install it with the recommended settings. It can automatically detect problems with older programs.

The Program Compatibility Assistant detects known compatibility issues in older programs. After you have run an older program in this version of Windows, it notifies you if there is a problem and offers to fix it the next time you run the program. If the compatibility issue is serious, the Program Compatibility Assistant might warn you or block the program from running. If that happens, you’ll have the option to check online for possible solutions.

Changes made by Compatibility Assistant: It depends on the problem, but any changes made are related to how Windows runs the program. No changes are made to the program, itself. For example, the Program Compatibility Assistant can resolve conflicts with User Account Control, a security feature in Windows that can help make your computer safer. Or, it can run the program in a mode that simulates earlier versions of Windows. The changes that Program Compatibility Assistant makes are done automatically, so you don’t need to make them.

Changing the settings of Compatibility Assistant: Adjustments to program compatibility features can be made by using Group Policy. You can’t be able to run it manually, The Program Compatibility Assistant runs automatically when it detects an older program that has a compatibility problem. However, you can use the Program Compatibility troubleshooter, a separate feature of Windows 7, on a program or on a setup file if it won’t work or install correctly.

To use Program Compatibility Troubleshooter, follow these simple steps:

  1. Go to Control Panel, Open Troubleshooting (if All control Panel items are showed) otherwise search for Troubleshooting.
  2. In Troubleshooters list, select the Programs troubleshooter (Check the highlighted option in the screenshot below).
  3. Select it and follow the simple steps showed in the wizard window of troubleshooter.

To disable it, you may Disable Program Compatibility Assistant Service via services.msc or Turn off Program Compatibility Assistant setting via gpedit.msc.