Microsoft has announced via a blog that it will offer upgrades to Windows 8 for just $39.99 for anyone using an existing Windows 7, Windows Vista or Windows XP PC or laptop. Windows Media Center will be available free to upgraders, although it will require an additional software download.

Microsoft is obviously keen that existing users get Windows 8 via a download, as upgrading with a physical Windows 8 disc will cost $69.99 (around £45).

All of this suggests that it will cost around £25 to upgrade to Windows 8 with Media Center, although it remains to be seen whether UK users will be able to get the upgrade at the same price as our US cousins. Typically, UK prices are higher than US, due to the demands of localising an OS for a smaller market, and because tax is applied locally in the US.

In the blog post, Microsoft's Brandon LeBlanc says that the upgrade from Windows 7, Vista and XP will be a painless experience. It says that a Windows 8 upgrade assistant wizard will pinpoint device or application incompatibility issues, and run you through the process step by step. To be fair, our experience of installing both the Consumer Preview and Release Preview has been impressively painless.

Windows 8 Upgrade Assistant "We set out to make it as easy as possible for everyone to upgrade to Windows 8," Le Blanc writes. "Starting at general availability, if your PC is running Windows XP, Windows Vista, or Windows 7 you will qualify to download an upgrade to Windows 8 Pro for just $39.99 in 131 markets. And if you want, you can add Windows Media Center for free through the 'add features' option within Windows 8 Pro after your upgrade.

"When you use to purchase an upgrade to Windows 8 Pro, the Windows 8 Upgrade Assistant makes upgrading simple by walking you through the upgrade process step-by-step from purchase to download and then of course installation."

Further good news about upgrading to Windows 8, is that Microsoft says that Windows 7 and Vista users will be able to upgrade and retain files, applications and settings, and even Windows XP users won't have to lose any files.

"Of course, if you want to start fresh, you can choose to bring nothing along. Or if you prefer to format your hard drive as part of your upgrade experience, you can do so as long as you boot from media and then format your hard drive from within the setup experience for installing Windows 8, not prior to it," the blog post says.

This upgrade promotion for Windows 8 Pro both online and in stores runs until January 31, 2013.

For more on the changes in Windows 8 and how to use them visit Windows 8 Advisor. (See also: Windows 8: the complete guide.)