AARD code
The AARD code was a segment of code in a beta release of Microsoft Windows 3.1 that would issue a cryptic error message when run on the DR DOS operating system rather than the Microsoft-affiliated MS-DOS or PC DOS. Microsoft inserted the code in an attempt to manipulate people into not using competing operating systems; it is an example of the company's fear-uncertainty-doubt tactics. == Description == This XOR-encrypted, self-modifying, and deliberately obfuscated x86 assembly code used a variety of undocumented MS-DOS structures and functions to detect if a machine was running DR DOS. The code was present in the installer, in the WIN.COM file used to load Windows, and in several other EXE and COM files within Windows 3.1.