Microsoft intends to spend $500m (£285m) marketing its software systems to business users over the next year.
The announcement, which aims to win trade at the expense of IBM, was made by chief executive Steve Ballmer.
He said the firm's latest Microsoft Office and Windows Mobile systems meant companies could now do the tasks they previously paid IBM to do for them.
IBM dismissed Microsoft's announcement as "window dressing", saying it was not driven by consumer needs.
'Empowerment'
Mr Ballmer was speaking at a press event in New York.
"Getting the most out of their people is on the mind of every business leader I speak with," he said.
"[We] are passionate about the idea that the right software can provide the tools to empower workers to become the drivers of business success."
IBM responded by saying Microsoft's plans were "product-driven instead of customer-driven".
"It's clear, our survey of some 700 chief executives indicates that business process and business model innovation is what matters most to clients, and that can't be achieved by another proprietary piece of software," IBM added.
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