Thursday, 7 Dec, 2017 The installation failed in the SAFE_OS phase with an error during PREPARE_FIRST_BOOT operation Fix. Make sure that your device has enough space. Your device requires at least 16 GB of free space to upgrade a 32-bit OS, or 20 GB for a 64-bit OS. For more info, see Free up drive space in Windows 10. SRC: https://support.microsoft.com/en-au/help/10587/windows-10-get-help-with-upgrade-installation-errors 3/5 - (55 votes) Andrea MatesiSenior Professional Network and Computer Systems Engineer during work hours and father when home. Andrea strives to deliver outstanding customer service and heaps of love towards his family. In this Ad-sponsored space, Andrea shares his quest for "ultimate" IT knowledge, meticulously brought to you in an easy to read format. Share this:LinkedIn Related