Microsoft has amended the terms of service for Windows Vista following an outcry from users who feared that the operating system would limit the ability to upgrade their PCs.

The controversy was sparked by a section of Microsoft's End User Licence Agreement for Windows Vista which read: "The first user of the software may reassign the licence to another device one time."

Users upgrading components in Windows XP are often prompted to re-enter their activation keys for Windows. This has led to some users needing to re-activate the product several times.

This was not a problem as XP does not limit the number of times a user can activate the software as long as it was removed from the previous device.

The passage in the Vista agreement led bloggers to question whether they would need to purchase a new licence if their motherboard failed, for example, or if they had to replace a hard drive or other component. 

Microsoft has since changed the wording on the agreement to specify that users can move the software onto another device.

"You may uninstall the software and install it on another device for your use," the agreement now states. "You may not do so to share this licence between devices."