Alongside plans to double its network to 80 outlets within the next three years, PC World will create more than 4,000 jobs.
Customers will be able to order products over the phone after studying a 692-page catalogue, which is a techies' dream, containing more than 9,500 computer products.
Terry Duddy, managing director of PC World, said: "This is a huge market which we want to exploit.
"The British IT business is worth pounds 6bn a year and is showing an annual growth rate of 10 per cent."
Dixons plans to launch a multi-million pound advertising campaign to promote the mail order service to its 20,000 business customers. Altogether it will spend about pounds 16m on the new business and at least pounds 75m expanding the PC World chain.
Dixons' move will be a blow to Action Computers, which runs the UK's largest computer mail order business.