Microsoft announced two changes for Windows Phone owners today, ones that “most of you likely won’t even notice” according to a blog post on the Windows Phone blog.  The first removes the ability to purchase Windows Phone apps from within the Zune PC software, which seems to be being phased out in favor of the Windows Phone Marketplace (or Windows Phones themselves), but is still required to update and back up your Windows Phone.  The second change will soon require that users run Windows Phone 7.5 (Mango) to be able to update or install apps, or even to submit app reviews.

Probably the next time you fire up your Zune PC software (as we just did), you’ll get a “features have changed” notice:

… and the ability to purchase Windows Phone apps will be gone from Marketplace>Apps.  As we said, you can still buy apps either from your phone or from the Windows Phone Marketplace, including Fruit Ninja for 99 cents, or any one of 80,000+ apps.

As for upgrading your phone to Mango, we hope you’ve done that long ago, but in case you haven’t, you can learn more about the update process, and then update your phone, using this guide.  It should take about an hour.