Microsoft has started rolling outWindows 10 14390 Insider Preview to PC and Mobile devices. The new Preview build is available to the Insiders in the Fast ring, who can now start testing the latest Insider build.Windows 10 14390 has brought in a new Edge extension, along with a number of new fixes and improvements. Of course, we don't expect to see any new features since we are almost at the end of the development process.

There has been reports that Windows 10 14390 could be the build that will be rolled out to the public on August 2, meaning this is the RTM (or Release to Manufacturing) build. With still over two weeks to go,we will see if there is a couple of more Preview builds coming to Insiders next week. Seems unlikely, however, especially sinceDona Sarkar insisted todayto "install this build and try things differently than usual this weekend."

Following are the improvements and known issues (seriously!) in the PC and Mobile builds. There are three known issues in the latest build of Windows 10 Mobile, and it seems Microsoft will roll out fixes via itsStore, which meanswe won't need a new build to fix these.

Improvements and fixes for Windows 10 14390 PC

You should no longer see the error code 0x80004005 when enabling Developer Mode on the “For Developers” Settings page if your PC is using a non-EN-US language.

Known issues for PC

AWARENESS: A recent fix went into place for the Hyper-V firmware that will that affect the ability to boot Windows Server 2016 Tech Preview 5 VMs with Secure Boot enabled. A fix for TP5 builds has been developed however, due to release schedules, the Insider Preview build changes will be released before the TP5 fix is released. During that time, if you try to boot a new TP5 VM with Secure Boot enabled, it will fail. The workaround is to disable Secure Boot during this period.

Known issues for Windows 10 Mobile 14390

Voice Recorder does not show up consistently as an option for Call Recording. We heard your feedback and plan to release a Voice Recorder app update via the Store soon that has the fix for this issue.

Wallet users are prompted for a PIN twice when using tap to pay from a locked phone.

You can enter their PIN twice and tap as usual once the phone is unlocked. A fix for this will come as a Wallet app update via the Store.

Once you install and test this latest Preview build, don't forget to share with us if you think the operating system is ready for the public use.