Microsoft on Friday let users who want to upgrade from one version of Windows 7 to another know how they can do so.

The company also unveiled pricing for the previously announced Windows 7 Family Pack, a version of the OS for households with multiple PCs. The family pack allows people to upgrade three PCs from earlier versions of Windows to Windows 7 Home Premium for $149.99, saving more than $200, Microsoft said. An upgrade to Windows 7 Home Premium for one machine costs $119.99.

[ Test Center: Windows 7 RTM finally arrives, and the time is ripe for an upgrade. ]

Microsoft expects many people will purchase their preferred version of Windows 7 when they buy a new PC with it pre-installed, and is already allowing people to pre-purchase Windows 7 -- which is scheduled to be available globally Oct. 22 -- through a Technology Guarantee Program when they buy new PCs now.

However, for those who purchase Windows 7 but then want to upgrade to a version with more features, Microsoft is offering a Windows Anytime Upgrade program, which can be launched from within Windows 7, the company said.

Once Windows 7 is available, people in the U.S. can buy a retail package that contains an upgrade key, which will give them the ability to upgrade on any of three paths: from Windows 7 Starter to Windows 7 Home Premium for $79.99; from Windows 7 Home Premium to Windows 7 Professional for $89.99; and from Windows 7 Home Premium to Windows 7 Ultimate for $139.99.

People can use the key to upgrade through a series of screen prompts on their Windows 7 PC; the process takes about 10 minutes and will not disrupt a user's current programs, files or settings, Microsoft said.

In Australia, Belgium, Canada, France, Germany, Italy, Japan, the Netherlands, Spain, Sweden, Switzerland, the U.K. or the U.S., people can purchase the upgrade from Microsoft online directly within Windows 7.

By way of comparison, upgrade pricing from an earlier version of Windows, such as XP or Vista, for Windows 7's consumer versions is: $119.99 for Windows 7 Home Premium; $199.99 for Windows 7 Professional; and $219.99 for Windows 7 Ultimate.

Microsoft envisions several scenarios in which customers may need to upgrade from one version of Windows 7 to another. For example, a person may purchase a netbook with Windows 7 Starter on it primarily to use the device for e-mail, but then find it's more suitable as an everyday PC. In that case, the user may want to upgrade that netbook to Windows 7 Home Premium, the company said.

For a person running Windows 7 Home Premium, upgrading to Windows 7 Professional would give them the ability to join a business network and also take advantage of a feature called Windows XP Mode that allows them to run applications written for Windows XP on a Windows 7 PC seamlessly, Microsoft said.

Windows 7 Ultimate is the most fully featured of Microsoft's consumer OSes and includes security features that some power home users might want, the company said.