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The company announced last week that it was launching Windows 7 Starter Edition as a low-cost option designed specifically for netbooks.

However, the company's decision to impose a three-app limit could force many manufacturers to opt for the more expensive Home Premium.

The three-app rule includes applications running in the background, meaning that a user running Windows Messenger and Skype, for example, could only use one further application on their machine. Antivirus software is excluded from the app count.

Microsoft says the restriction is designed to ensure that users get the best possible performance from limited netbook hardware. However, it admits it will encourage netbook manufacturers to install the unrestricted Home Premium in the UK.

"It's up to the OEMs to decide on whether or not they actually pick Starter edition or Home Premium," Windows product manager, Laurence Painell, told PC Pro.

"We would obviously recommend they use Home Premium in the UK because we find the netbooks we have here are of a higher spec, but it's up to them which one they pick."

PC Pro has installed Windows 7 Ultimate on two different netbook models, and found performance is largely unencumbered by running multiple applications. The netbooks were even capable of running advanced features such as Windows Media Center comfortably.

Microsoft denies that it's imposing an arbitrary application limit on Starter Edition to force manufacturers to adopt the more expensive Home Premium. "We need to make sure there's a clear differential between Starter Edition and Home Premium and make sure that the choice that the OEMs have got is very clear and allows them to make that

"We expect to see that OEMs will pick Starter Edition for lower form-factor netbooks and then maybe pick Premium for some of the better-spec netbooks."

The company claims most users wouldn't be affected by the three-app limit. "We ran a study which suggested that the average consumer has open just over two applications [at any time]," Painell claims. "We would expect the limit of three applications wouldn't affect very many people."

However, Microsoft told journalists at last year's Professional Developers Conference that 70% of Windows users have between eight and 15 windows open at any one time. "That's probably talking across all users," Painell says. "That's talking across enterprise and business as well, which is a very different segment."

Upgrade options

Even if manufacturers do decide to opt for the restrictive Starter Edition to save costs, users will be able to upgrade to Home Premium by simply buying a product key for their netbook.

Microsoft - which is currently being sued in the US for allegedly misleading customers with the Vista Capable sticker scheme - says it is working with manufacturers to make sure the three-app limit is made to clear to buyers at the point of sale.

"It is very clear in all the differentiating features we provide to them... that it will only support up to three concurrent applications," Painell says. "We're making sure that message goes out to all of our partners. We'll be working through them to make sure advertising goes out correctly to the wider audience."

Starter Edition was limited to running three concurrent applications in Windows Vista, but that version wasn't available for sale in the UK.

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