Before you go have a look of this:
Protect your PC and data. Ensure that backup has been taken.
Activate the product:. Activation neccessary within 10 days else system will shut down once every hour until activated.
Product key of Windows: No need of product key (it is embedded with the download).
The 90-day Trial will shut down once every hour when you have reached the end of the 90-day evaluation period.
Limited offer Download will be available through March 31, 2010, till supplies last.
After the 90-day Trial expires, if you wish to continue to use Windows 7 Enterprise, have to be purchased and then perform a clean installation of Windows 7, including drivers and applications.
Windows 7 Enterprise will be available in both tastes as 32-bit and 64-bit in five languages: English, French, German, Japanese, and Spanish.
Visit Microsoft Technet for download.