Numerous would-be Windows 7 users are reportedly suffering through installation failures when attempting to upgrade their computers to Microsoft's newest operating system.

Windows 7 screen shot
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The problem appears to arise mostly when users attempt to perform a so-called clean installation of the software onto a hard drive that's been wiped clear of existing data.

The bug doesn't affect Vista users, who can perform an in place upgrade to Windows 7 without impacting the contents of their hard drives. Instead, it afflicts Windows XP users, who must perform a clean installation in order to jump to Windows 7.

The problem: a Microsoft security feature in some cases won't allow installation of an upgrade version of Windows 7 onto a clean hard drive, because such versions are meant to be used only on machines with existing copies of Windows installed.

XP users, though fully entitled to use the less expensive upgrade-ware, are as a result seeing an error message when they enter their Windows registration number that in part reads, "The Software Licensing Service determined that this specified product key can only be used for upgrading, not for clean installations."

Fortunately, tech support staffers at various organizations have found an unofficial workaround that appears to neatly solve the problem.

XP users who are performing a clean upgrade to Windows 7 are advised not to enter their product key when prompted during installation. Rather, they should move on to the next step and only enter the key once full installation is complete.

The method "works around this issue to activate Windows 7," notes a support bulletin published by the IT department at the University of Wisconsin-Madison, where numerous students were apparently having trouble with the issue.

For its part, Microsoft has not published an official solution to the problem—possibly because any fix might allow a user to illegally install an upgrade version of Windows 7 onto a PC that's not eligible for an upgrade. The temptation is strong, given that the upgrade version of Windows 7 sells for $119, while the full version is priced at $199.

Despite the installation glitch, Windows 7 appears to be faring well in the market. New figures released by Net Applications show that the OS's share of the computing market jumped to from 1.89% on Oct. 22nd, the day of its release, to 3.67% as of Sunday.

InformationWeek has published an indepth report on Windows 7. Download the report here (registration required).