Hewlett-Packard offered to buy British software company Autonomy for $42.11 a share, or $10.2 billion.
The company may also spin off its PC unit and said it will discontinue the WebOS-based TouchPad tablet computer and phones.
The company, which was expected to report earnings after the bell, delivered its results an hour early. The second-quarter results hit expectations but its outlook disappointed.
Its shares were briefly halted pending the news, then fell when they resumed trading.
The tech giant said its fiscal third-quarter earnings excluding items rose to $1.10 a share from $1.08 a share a year earlier.
Revenue rose to $31.2 billion from $30.7 billion a year ago.
Analysts had expected earnings of $1.09 a share on revenue of $31.2 billion, according to Thomson Reuters.
The company's outlook fell short of expectations: HP projected earnings excluding items of $1.12 to $1.16 a share for the fiscal fourth quarter and revenue of $32.1 billion to $32.5 billion. The earnings include about 61 to 68 cents a share in restructuring costs.
Analysts are expecting earnings of $1.31 a share on revenue of $34 billion for the fiscal fourth quarter.
Shares of HP, a storied Silicon Valley icon that dominates the personal computing industry, were briefly halted pending the news, then fell about 7 percent following the announcement.
The company is expected to announce a long-rumored spinoff of its PC division, the world's largest. A spinoff of HP's PC arm would confirm speculation that has swirled for months that HP was no longer keen on keeping a business struggling with low growth and single-digit margins.