For those waiting, Microsoft has unveiled a 90-day free trial beta version of its desktop OS Windows 8 released to manufacturing (RTM). This early look of the OS is offered for PC manufacturers and developers of Windows apps.

The Windows 8 operating system is believed to hit shelves October 26 and in order to get ready; Microsoft has to give several parties copies of the OS. The company received a USB drive with RTM, which they are currently testing.

As for now, this version looks same as the Release Preview. However, there are minor changes Microsoft had made, which include a non-Aero desktop and a choice of performance tweaks.

While this version is considered an important upgrade from Windows 7, whether it’s worth $40 is something that we will have to wait to watch.

Besides the RTM release, Microsoft has made the download of this 90-day trial version of Windows 8 Enterprise open for all. System requirement of this version is same as that for Windows Vista and Windows 7.

However, this 90-day free trial comes with a lot of drawbacks. Microsoft says that this evaluation edition will expire after 90 days and cannot be upgraded. And once it expires, the computer screen will go blank and PC will shut down every hour to prevent users from using it. To upgrade, users will have to uninstall the evaluation, reinstall a nonevaluation version of Windows from the original installation media.

Microsoft also points out that users must run the evaluation edition in a virtual environment or install it on a separate hard drive or partition to upgrade original Windows installation to Windows 8.

During registration of this free trial version, users will have to log in with a Microsoft account and provide their name, e-mail address, and country. It also needs users to activate the product online within 10 days of installation.

Once the evaluation is installed on a PC, it cannot be upgraded. When users want to revert to a previous version of Windows, they will have to do a clean install from the original installation media.

Basically, it is recommended that Microsoft Windows 8 Enterprise should be downloaded only by those who are okay with reinstalling Windows after the trial period gets over.