Steve Ballmer will host Microsoft's biggest ever launch event later today, with the combined releases of SQL Server 2005, BizTalk Server 2006 and Visual Studio 2005.

The software giant will host 300 events in 89 countries to present the new code to 190,000 developers and potential clients.

All attendees will be eligible for a refund on the cost of developer certification examinations in the new code.

Microsoft is also releasing cut down versions of SQL Server and Visual Studio, labelled 'Express', which will be available as a free download from the Microsoft website.

This is an attempt to get more hobbyists and non-developer enthusiasts to use the code, of which there has already been over a million downloads of the preview version.

"We have development tools for professional developers but we're also extending out the code for hobbyists," said Andy Lees, corporate vice president for server tools and marketing at Microsoft.

"There are 10 million hobby developers out there and we want to cover that customer segment. It's about extending across the whole IT community."

Visual Studio Express was going to be priced at $49 but the company decided at the last minute to make it free for the first few months after the launch.