Install From an Upgrade Disc

Past Windows versions have let you prove upgrade-readiness by inserting a CD of the previous OS during the install process. Vista doesn't; Microsoft specifically says "Windows Vista does not check upgrade compliance. Therefore, you cannot use an upgrade disc to perform a clean installation of Windows Vista." To work around this problem, insert your CD into your clean computer. Don't enter the code when Vista asks for your license key, simply click Next. You'll create a system sans activation code that's active for 30 days. Then reboot from the CD; you'll be able to install the OS as an update to your Vista installation. Now use the activation code.