14 DAY TRIAL // With Windows Vista, Microsoft has limited the upgrade process of the operating system. Unlike past versions of Windows, Vista does not simply require the user to pop in the media with the prior version of the operating system from which the upgrade is performed. In fact, Microsoft has built Vista so that it will only upgrade from an already installed and genuine version of Windows. In this regard, Microsoft has informed that users will not be able to use an upgrade key in order to perform a clean installation of Windows Vista.
However, there is a workaround available that will bypass the fact that Windows Vista does not check for upgrade compliance. By applying this method to the installation, you will be able to do a clean install of Windows Vista with an upgrade license key, and it does not require users to have an older version of Windows in place.
First off, you have to install Windows Vista. Do so from the upgrade DVD you have purchased. Boot from the Windows Vista Upgrade DVD and follow through with the setup program. However, do not enter your product key when the operating system asks for it and simply click next. In this manner, you will be able to install the operating system with a 30 days Initial Grace period.
Once you have completed the deployment of Windows Vista, run the installation program again from within the operating system. The only difference is that this time around, you will enter the upgrade license key you have purchased.
Choose to perform a Custom (advanced) installation of the operating system and not an Upgrade when prompted, and install the operating system all over again. When the setup process will end, activate your upgrade copy of Windows Vista normally. Additionally, you will be able to remove the Windows.old file in order to erase all traces of the first Vista install.