In September of last year, just prior to the operating system's official debut, Microsoft launched a limited-time offer allowing customers to try Windows 7 Enterprise for free. Citing popular demand, the company has extended that program until the end of 2010. Customers now have until December 31 of this year to download and evaluate the OS.
Being an Enterprise edition, Microsoft suggests that only IT professionals should sign up, but it seems anyone is eligible. No product key is required to install the trial copy as it's embedded in the download, and both 32 and 64-bit builds are available. Upon installation, you'll have 10 days to activate the product, or the system will shut down once every hour until activated.
The system will also power down every hour after the 90-day trial period expires, at which point you'll need to purchase a license and perform a clean install of Windows 7 -- drivers and applications included. Head over to the TechNet Evaluation Center for more information.