Internet retailer Amazon.com Inc. has started taking early orders for Microsoft's long-delayed Windows Vista operating system, offering versions of the product from $100 to $399.

The retailer's Web site said the software will be available on January 30, and an Amazon spokesman said on Tuesday the date was an estimate based on informal conversations with Microsoft and others in the computer industry.

Microsoft has not yet commented on Amazon's pre-sale, saying the software maker is still finalizing its pricing model. It has not set a release date for the new version of Windows, which sits on more than 90 percent of the world's personal computers.

Microsoft has repeatedly postponed the release of Windows Vista, which is already five years in the making. Quality assurance delays have put off the consumer version of Vista until early 2007 -- after the crucial holiday shopping season. Vista is due to ship to corporate customers in November.

Amazon's pricing ranges from $100 for a basic upgrade version of Windows to $399 for a full "ultimate" version of the operating system, according to the retailer's Web site.

A January 30 release date would be about two months ahead of what it was initially expected.