The message, sent by the head of the Windows Development at the time, David Cole, to another executive, could be pivotal to a private antitrust lawsuit against Microsoft pending in Utah. It may also surface in the US government's latest suit against the company, which comes to trial next month.
The worry for Microsoft back in 1991 was that computer makers as well as consumers should be persuaded to adopt Windows in conjunction with the company's older system, MS-DOS. Above all, it is alleged, it wanted to repel the threat of DR-DOS, a near-identical system created by a software rival, Novell.
The sabotage idea came about during a drinking session among Microsoft engineers, at least according to Mr Cole's e-mail. A colleague, he said, had had "some pretty wild ideas after three or so beers".
Wildest of all, apparently, was the notion of a bug that would "put our competitors on a treadmill" and "should surely crash at some point shortly later".
The memo then goes on to advise strict secrecy. "The less people know about exactly what gets done, the better," Mr Cole wrote.
Microsoft has since confirmed the existence of the e-mail, which is among thousands that were subpoenaed by the Justice Department in an earlier 1995 lawsuit against the company and which may be used again in the government's fresh suit.
The government has accused Microsoft of unfairly squeezing its competition to maintain its iron-like grip on the software market for home PCs.
It has also claimed specifically that Microsoft acted to nobble its most dangerous rivals in the design of its products and through exclusive licensing pacts.
The private suit has been filed by little-known Caldera, a company that has since bought the DR-DOS technology from Novell. It alleges that the offending bug was deliberately inserted into a test version of the new Windows system that was distributed to program developers and PC manufacturers in 1991.
The alleged mission of the bug was to identify any time that Windows was being super-imposed on a DR-DOS platform instead of Microsoft's own MS-DOS. Moreover, if DR-DOS was identified it was meant to freeze the computer and display a message urging the user to contact Microsoft.
The hoped-for result is made clear in another Microsoft memo that will also appear at the Caldera suit. "What the guy is supposed to do is feel uncomfortable when he had bugs, suspect the problem is DR-DOS and buy MS-DOS and not take the risk," the memo, dated 10 February 1992, states.
Microsoft has essentially admitted that the bug existed in the test versions of Windows though not in versions then shipped to the public. A spokesman told The Wall Street Journal this week that in the test version, "we had code designed to help reduce product support costs ... in the end even that limited function was disabled before it was released to consumers".