From Monday search engine firm Google will launch a global advertising campaign to wean businesses off Microsoft and onto Google Apps.
The move comes after Google announced that more than two million businesses and 20 million people in 100 countries had signed up to use Apps as their workplace software.
Among the larger companies to go with Apps are hygiene firm Rentokil, the Guardian and Telegraph newspaper groups, image processing firm Konica Minolta, and US-based pharmaceuticals maker Genentech.
Under the banner "Gone Google" the search firm is extending its advertising campaign to the UK, France, Canada, Japan, Australia and Singapore.
Google will display messages in train stations such as Paddington, La Défense and Shinagawa, and at airports in Singapore, Toronto, Dallas and other venues.
It has also set up a Twitter feed so that firms that have already opted for Apps can share experiences.