-- Home Premium to Ultimate $159

-- Business to Ultimate $139

Moreover, after the upgrade, users who originally owned an OEM version of Vista will own a full retail version of Vista, the Microsoft spokeswoman said.

Retail versions of Vista generally allow users to install the operating system on another computer if the first one dies, though only one such transfer is allowed.

OEM versions of Windows are tied to the original computer it was installed on. Microsoft does not allow users to transfer OEM copies from one computer to another, even if the original one crashes and dies.