Users of the Windows Marketplace app store will soon need to have the latest 7.5 version of Windows Phone installed on their devices in order to download, update or review apps.

Writing on the Windows Phone blog, Microsoft’s Mazhar Mohammed explained that the rapid growth of Marketplace, which will soon be available in 63 countries, means the newer software is needed to improve performance and security, “paving the way for even faster growth and more new features.”

Mohammed said most Windows Phone users will already be on the latest version of the OS but a “handful of folks” haven’t yet upgraded.  “If you’re one of them, and you like apps, now would be a good time to update,” he wrote. The requirement to have Windows Phone 7.5 will come in over the next few weeks.

In addition, the option to browse and buy Windows Phone apps using the Zune PC software is being removed. “As a general rule, we like to focus our engineering efforts where they matter most, and your taps and clicks tell us that’s our phone and web stores,” Mohammed said. He added that the Zune HD app store for Zune portable entertainment devices will remain open.

Microsoft’s Todd Brix wrote on the Windows Phone Developer Blog that the loss of ability to manage apps through the Zune technology will make it important for developers to use the correct protocol or ‘deep link’ for direct links to apps in Marketplace.
If developers use the older zune:// format for links, customers will receive an error message.

Brix added that the OS software required for customers to access Windows Marketplace in nine additional markets has been released. Although developers have been able to submit apps for Bahrain, Israel, Iraq, Kazakhstan, Qatar, Saudi Arabia, Thailand, UAE and Vietnam, customers have been unable to access the app stores.