Microsoft, the world's largest software maker, says it is giving businesses a preview of the next version of its operating system, Windows Vista.
Windows software runs on 90% of personal computers worldwide
The new version is being tested with 500,000 customers, it said.
The software, previously known by its code name Longhorn, is due for release towards the end of 2006, half a decade after the launch of Windows XP.
Microsoft says the system will make it easier and less expensive for firms to keep their computer networks secure.
The new system will feature safer web browsing with the inclusion of Internet Explorer version 7, the software giant said.
Brad Goldberg, general manager for Windows product management, said Vista would allow people to log on to their office's system remotely without needing to connect through a virtual private network, or VPN.
Other features will include easier installation of software fixes, known as patches, to protect computers from viral attacks.
Changes to user-account controls, it said, would make it harder for viruses to spread around office networks.
Once Vista hits the market it will be the longest gap between releases of Windows systems.