Microsoft has yanked a tool it touted as a way for netbook owners to install Windows 7 without a DVD drive after a prominent blogger accused the company of using open-source code without acknowledging where it originated.

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The free utility, Windows 7 USB/DVD Download Tool (WUDT), has been pulled from Microsoft's site, as has the page of instructions on how it was to be used.

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Microsoft released the Download Tool last month, and at the time trumpeted the utility as a workaround that would let netbook owners create a bootable flash drive from a downloaded .iso file, or disk image, of Windows 7 purchased from Microsoft's online store.

"We are currently looking into this issue and are taking down WUDT from the Microsoft Store site until our investigations are complete," a Microsoft spokeswoman said in an instant message reply to questions Tuesday. "We apologize to our customers for any inconvenience."

Microsoft's move was prompted by Rafael Rivera's claim last Friday that WUDT included code gleaned from a GPLv2-licensed open-source project. Rivera, who writes the Within Windows blog, said Microsoft had "obviously lifted" code from the ImageMaster project, and had then compounded the problem by not sharing the source code for its modifications, or the tool itself, to the project, as required by the terms of GPL (GNU General Public License).

GPL is a widely-used free software license that was originally drafted by Richard Stallman of the GNU project.

Microsoft has previously released several code modules under GPL, including the Live Services Plug-in for Moodle last July.

Today, Microsoft declined to answer questions about the future of WUDT, including whether it would re-release the tool at some point, and whether the utility had been removed from its site because of the GPL brouhaha that Rivera instigated.

Rivera said he was "99.9999% sure" that Microsoft used the open-source code within WUDT, and provided code examples to prove his point.

"I'm not a GPL expert -- the thing reads like Latin -- but it is my understanding that the tool would have to be open-sourced, as required by GPL," Rivera said today in an interview conducted via instant messaging.

Actually, the algorithm in question originated with the open-source file archiving software, 7zip, which is licensed under the LGPL, or GNU Lesser General Public License, a software license published by the Free Software Foundation, said Rivera. Microsoft's tool grabbed code from the GPL-protected ImageMaster project, however.