Palo Alto, Calif.--In a deal that would change the global consulting landscape overnight, Hewlett-Packard Co. is in talks to buy PricewaterhouseCoopers L.L.P.'s consulting unit for up to $18 billion. The unit, the world's largest consultancy, has in the last several years become a b-to-b powerhouse, advising Fortune 500 companies and start-ups alike on their Internet marketing, technology and strategy. HP would overnight become one of the most powerful forces in consulting, raising questions about how a company whose core business is making and selling hardware and software would maintain an unbiased outlook when recommending platforms to its consulting clients. HP's move comes as consolidation and globalization sweeps the consulting industry; earlier this year, Paris-based Cap Gemini SA bought Ernst & Young L.L.P.'s consulting arm.