U.S. percentages were generally higher than those in the U.K., where the same system costs £340.99. British buyers must fork over 21% of that to upgrade from Starter to Home Premium, 41% to move from Starter to Ultimate.

EU consumers will be hardest hit. Although the Starter-to-Premium Anytime Upgrade accounts for 19% of the €399.95 cost of the netbook -- less than the percentage U.S. buyers pay for the same upgrade -- Starter-to-Professional and Starter-to-Ultimate consume 46% and 51% of the ASUS machine's price, considerably more than the 35% and 41% U.S. users would have to fork over.

Even paying less than consumers in the U.K. and the EU, U.S. users may not find Microsoft's Anytime Upgrade prices attractive. At suggested list prices, there's only an $80 difference between the retail copies of Home Premium Upgrade and Professional Upgrade, and $100 between the two "Full" editions. The Anytime Upgrade from Home Premium to Professional, meanwhile, costs $90.

It's even less enticing to take the Home Premium-to-Ultimate path using Anytime Upgrade. Microsoft's priced that at $140, higher than both the $100 difference between the retail Home Premium Upgrade and Ultimate Upgrade, and the $120 difference between the "Full" editions of those versions.

At least one analyst has dinged Microsoft for the . "Microsoft needs to be more aggressive," Stephen Baker, an analyst with the NPD Group, said in an earlier interview. "At those prices, there won't be many opportunities to [convince users to] trade up. If people are buying cheap [PCs] they're buying cheap for a reason."