Microsoft today opened its virtual store and began selling upgrades to Windows 8 Pro for $39.99, making good on a promise made last summer.
The upgrade, which must be downloaded and installed via a utility called "Windows 8 Upgrade Assistant," can be applied to Windows XP-, Vista-, and Windows 7-powered systems.
Microsoft announced the upgrade in July, a bit more than a month after it issued the last of three public previews, but before it wrapped up its work on the new OS.
The upgrade does the most thorough job when migrating a machine from Windows 7, which is the only edition that conducts a "full" upgrade, the label for an upgrade that brings along everything, including data files, user accounts, Windows settings and installed applications.
Windows XP-to-Windows 8 upgrades are the least comprehensive, allowing customers to move only personal files; Vista transfers both Windows settings and personal files to Windows 8.
Although the $39.99 buys only the upgrade's 2GB digital download, users can optionally request a DVD for an additional $14.99. The combination is about $15 cheaper than the $69.99 DVD-in-a-box that Microsoft and retailers, including Best Buy, Wal-Mart and Amazon, are now selling.
Microsoft has said that customers who downloaded and installed the free "Windows 8 Release Preview" will be able to upgrade to the paid version of the OS, but that those running the free trial of Windows 8 Enterprise RTM, or "release to manufacturing," which debuted in August, cannot.
That was just one of the problems reported by customers.
In messages on Microsoft's support forum, several said they had been blocked from upgrading by a confusing error message. "Windows 8 isn't available for download," the message stated. "Sorry, Windows 8 isn't available for online purchase in the country/region you're in."
Computerworld ran into the same message when it tried to purchase the Windows 8 Pro upgrade from a virtual machine (VM) running an evaluation copy of Windows 8 Enterprise. The VM was located in the U.S., where the upgrade is currently available, and the attempt was made after Microsoft turned on the upgrade spigot.
Others, however, said that they had been thwarted from upgrading a Windows 7 PC with a legitimate license. "Quite frustrating seeing as many others are downloading it without a problem," noted someone identified as "_PhAzE_" on a support thread.
Additional complaints were lodged about the upgrade, ranging from machines that refused to download the file, payment problems, and invalid activation keys provided by Microsoft.
Customers can start the upgrade purchasing and installation process by heading to Microsoft's Web site and clicking the button "Download Pro for just $39.99."
Microsoft will sell the Windows 8 Pro upgrade at the discounted price until Jan. 31, 2013. It's not entirely clear what the price will be after the offer expires, but several online retailers selling the $69.99 boxed copy show that price as marked down from a regular price of $199.99.
See more Computerworld Windows 8 launch coverage including news, reviews and blogs.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, on Google+ or subscribe to Gregg's RSS feed . His email address is email@example.com.