The $14.25-a-share offer is 38.6 percent more than Opsware's $10.28 Friday closing price.

Opsware shot up $3.72, or 36.19 percent, on the news to close at $14 a share on the Nasdaq Stock Market.

Hewlett-Packard lost 11 cents, or 0.23 percent, to $48.43 on the New York Stock Exchange.

Opsware, of Sunnyvale, Calif., and its 550 employees will become part of HP's software business, the Palo Alto, Calif., company said.

Opsware Chief Executive Officer Ben Horowitz is expected to become part of HP's management.

The Opsware purchase is intended to help HP customers control "the increasing complexity and cost of managing the data center," HT Software Senior Vice President Thomas Hogan said.