.Free Windows Vista Enterprise product keys are not available for several reasons. Not only is Windows Vista Enterprise only available to companies or IT professionals that are Microsoft Software Assurance customers, but it is not sold to the public through the usual retail outlets and, furthermore,It does require a product key to activate but the product key can be entered through a network server instalation program.
Activation of business operating software such as Windows Enterprise involves installign and activating designated computers via a network connection or by logging into a company network with a username and password through the internet. It is therefore very unlikely that a free product key will be available as shareware on the internet for this piece of software.
According to the Information Services department of MIT University (kb.mit.edu/confluence/display/ist/Windows+Vista+Enterprise+E) Windows Vista Enterprise is different to previous versions of Enterprise that run on operating systems such as XP in that it does not require a product key at all. Instead the computer on which it is installed needs to be activated within a month of installation.
Failure to activate the computer within a 30-day period will result in the computer going into reduced functionality mode in which the user will be locked out and a reinstallation of the operating software may be required. This is because of the tightened security measures provided by Microsoft to avoid software pirating.
Another option may be to download a free trial of the latest version of Windows Enterprise from the Microsoft website. (technet.microsoft.com/en-us/bb403698.aspx) Currently this is Windows 7 Enterrpise but no doubt these will soon be superceded by another version of the popular operating system. Trials usually last for 90 days, after which users will be required to purchase the full product if they wish to keep using the software.
In the case of Enterprise, this may mean registering with them as an IT professional. More information can be obtained by visiting: technet.microsoft.com/en-us/evalcenter/cc442495