The company is offering Vista Ultimate buyers in the U.S. and Canada theof Vista Home Premium for $50 apiece. However, some early takers on the offer got product license keys that did not work.
The software maker told CNET News.com Friday that it is aware of the issue and is working to fix things.
"New product keys are on the way as of this afternoon to the small group of customers who have been affected," a Microsoft representative said in an e-mail. "We've also taken steps to ensure that the issue is resolved going forward."
The family pack option, billed as a limited-time offer, is a new option with Vista. Amid, the Microsoft operating system to consumers on Tuesday.
Darryl Whitworth, of Duncan, British Columbia, said he bought Vista Ultimate primarily for the family pack option, but got an error message when he tried to buy the additional licenses.
"I am not sure if I would have purchased the (more expensive) Ultimate version if this offer had not been available," Whitworth said in an e-mail interview.
Ultimate carries aof $399, or $259 for those upgrading from Windows XP or Windows 2000, as compared to the Home Basic and Home Premium options, which range from $99 to $159 for the upgrade and $199 to $239 for the full version.