Here's a response from AI, because I was too lazy to explain it myself:
Compatibility mode in Windows allows older software programs to run on newer versions of the operating system by simulating the environment of the original Windows version for which the program was designed. This emulation enables the program to function as if it were running on the older Windows version, bypassing potential compatibility issues with newer Windows features and APIs.
Key Techniques Used
- Registry Tweaks: Compatibility mode adjusts registry settings to match those of the target older Windows version, allowing the program to access and utilize system resources as if it were running on the original platform.
- DLL and System File Emulation: Compatibility mode substitutes newer system files and DLLs with older versions, ensuring that the program interacts with the system as it would have in the original Windows version.
- API Wrapping: Compatibility mode wraps newer Windows APIs with older API calls, allowing the program to communicate with the system using the same interface it would have used in the original Windows version.