Microsoft has written down the value of its online advertising firm aQuantive by a massive $6.2bn (£4bn).
As Microsoft initially bought the firm for $6.3bn in 2007, this write-down all but wipes out the value of aQuantive.
Furthermore, Wall Street was expecting Microsoft to report a fourth-quarter profit of around $5.25bn when they release their financial figures later this month, and so the aQuantive write-down will likely eliminate this profit.
In a statement released on Monday, Microsoft confirmed the move, saying that "the acquisition did not accelerate growth to the degree anticipated, contributing to the writedown."
Additionally, Microsoft has downgraded its forecast for future growth and profitability for all of its online services, which includes the Bing search engine and MSN internet portal. The statement said that the rate of growth in this area would now be "lower than previous estimates".
This news will not come as a surprise to Microsoft investors, who were already well aware that the aQuantive acquisition had not been as successful as anticipated.
Previously Microsoft's biggest acquisition before their $8.5bn buy-out of Skype last year, aQuantive was seen as an attempt to catch up with Google in terms of increasing revenue from search advertising, but it became a very expensive gamble that didn't pay off.