According to the BBC, the loss of $US492 million in the fourth quarter of the fiscal year came as a result of a writedown of the value of its online advertising business.
Microsoft took over an outfit named aQuantive in 2007, paying $US6.3 billion. In the latest quarter, it wrote down almost the entire price, wiping off $US6.2 billion.
But in its media release about the results, there was no mention of the loss.
Despite the historic loss, company officials were upbeat.
"We delivered record fourth quarter and annual revenue, and we're fast approaching the most exciting launch season in Microsoft history,” chief executive Steve Ballmer was quoted as saying.
"Over the coming year, we’ll release the next versions of Windows, Office, Windows Server, Windows Phone, and many other products and services that will drive our business forward and provide unprecedented opportunity to our customers and partners."
Despite continuing to record steady income from its older products, Microsoft has failed to make a dent in the mobile, tablet, search or music sectors.