Washington, Jul 20 (IANS): US computing giant Microsoft has reported the first unprofitable quarter since it became a public company in 1986 after it wrote down the value of its failing online ad business, reported RIA Novosti.

The loss of $492 million in the fourth quarter stems mainly from the company's acquisition of online ad service aQuantive for $6.3 billion in 2007, which failed to compete with rival Google Inc.

Despite the $6.2-billion non-cash adjustment on aQuantive value, Microsoft topped analyst's expectations by posting a 4 percent increase in revenue to $18.06 billion for the same period.

The company's shares went up 2.4 percent to $31.39 after the quarterly results were announced Thursday.

Investors' confidence in Microsoft is fueled by high expectations for its new Windows 8 operating system for PCs and tablet computers, its own tablet PC called the Surface, and a new edition of Microsoft Office to be released this fall.

"We're fast approaching the most exciting launch season in Microsoft history," Microsoft CEO Steve Ballmer said in the company's earnings press release.

Judging by previews, Windows 8 promises to be the most drastic overhaul of the popular Windows operating system since 1995 as it features a new look, thousands of innovations and, most importantly, could be installed on tablets and smartphones.