Microsoft and online retailers last week kicked off Windows 7 sales in the U.S., Canada and Japan, taking pre-orders at prices discounted by as much as 58% and zooming to the top of Amazon.com's sales.

The upgrade for Windows 7 Home Premium, priced at $49.99, immediately stormed to the top of Amazon.com's bestseller list. The $99.99 Windows 7 Professional Upgrade held the No. 2 spot in software, while Windows 7 Ultimate Upgrade, a $219.99 package that has

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