The business is understood to be worth around £10 million and involves marketing across all HP business units, including consumer, small- to medium-sized business and large enterprise. The display advertising element will involve campaigns scheduled to appear on Google.
The account was previously shared between Modem and ZenithOptimedia's digital agency Zed Media, which also pitched for the business.
Norm Johnston, the managing director of Modem Media London, said: "HP's decision is recognition that they are taking search marketing seriously and want to do more than bid management. They highlighted that they were looking for a strategic partner that can make search a critical part of the marketing mix."
Search takes an increasing proportion of digital marketing spend every year. Clients spent around £200m on search in the first half of 2005, according to the Internet Advertising Bureau.
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