On the eve of the Windows 7 launch last year, Microsoft offered IT pros a chance to evaluate Windows 7 Enterprise for a limited time. But this week, the software giant announced that the evaluation version would now be offered through the end of 2010.

The free 90-day trial version of Windows 7 Enterprise--your choice of 32-bit or 64-bit version--was originally offered "while supplies last," which is an odd limitation for a software download.

Functionally, Windows 7 Enterprise is identical to the high-end Windows 7 Ultimate version, but is sold for use in volume-licensing business environments only. One of the benefits of Enterprise, then, is that it includes access to the valuable BitLocker-To-Go portable drive encryption technologies, leading to one of my most popular tips from the Windows Weekly podcast: Users with the more mainstream Windows 7 Home Premium can install the Enterprise edition in a Windows Virtual PC virtual machine (VM), encrypt their USB memory keys with BitLocker-To-Go, then safely access them using their host OS going forward. If the keys get lost, the data is safe.

Now, that ability—along with general access to the Windows 7 Enterprise trial—is being extended through the end of 2010. "Due to popular demand, the Windows Enterprise Trial program has been extended," Microsoft's Stephen Rose wrote in a blog posting this week. "This means you now have till December 31, 2010 to download and evaluate the trial version."

Readers interested in the 90-day trial version of Windows 7 Enterprise should visit the Microsoft Springboard web site.

Thanks to ZD's Mary Jo Foley for tipping me off to the trial extension.