After Microsoft delayed the release of Windows 10 for Windows Phone 8.1 handsets, there are signs that it's finally ready to roll. The software giant has launched an internal beta for the Mobile Upgrade Advisor for Windows 10, as spotted by a Neowin reader. That's similar to the tool it used last year to prep PC users for Windows 10. According to the description, the app "will tell if your Windows 8.1 phone is eligible to upgrade to Windows 10 Mobile. It can also help free up space on your phone so you're ready to upgrade." It's still not available for the public to download, but that situation should change soon.