In one beta release of Windows 3.1, Microsoft included hidden code (later called the AARD code) that detected DR DOS and displayed a cryptic error message. Although this code was not enabled in the final version of Windows 3.1, it gave the wrong impression that DR DOS was incompatible with MS-DOS and Windows among testers. These activities came to light when the discovery process of the subsequent lawsuit uncovered emails from senior Microsoft executives that showed this time bomb plant was part of a concerted program to drive Digital Research out of the PC operating systems business.
