Microsoft has released Windows 7 and Windows Server 2008 to manufacturers.
The software will be tested by hardware suppliers including Dell and HP. It remains on schedule to be made available to the public on 22 October.
Microsoft said the release is the culmination of a rigorous engineering project.
The company said it has had feedback from 10 million consumers and 4,000 IT professionals on the new operating system.
Jim Ginger, director of services at Dell, said Microsoft has never worked as closely with its OEM partners before. "Dell and Microsoft never had tighter integration in testing and getting systems ready," he said.
Microsoft is hoping businesses that were unhappy with their existing applications being incompatible with Windows Vista, will move to Windows 7, which should be more compatible.
It has developed a Windows XP virtualisation technology called XP Mode that will allow users to continue running XP applications on Windows 7, something that was not possible under Vista.
Users will also be able to run federated searches across their local hard discs, corporate intranet and the internet.
Other enterprise features include Direct Access, which, Microsoft says, will allow users to work from outside the company firewall without requiring virtual private network access.
Customers using Vista in Europe will not be able to upgrade directly to Windows 7. They will have to do a clean install.