The Flex OS installer erases the whole disk - Windows, partitions, files, everything on that drive. Here is what that really means, the backup checklist to finish first, and the honest route back if you change your mind.
Every Flex OS tutorial, including the video, reaches a calm little warning screen during installation and clicks through it in seconds. Slow down at that screen. The ChromeOS Flex installer erases the entire disk - it is a replacement, not an upgrade and not a dual boot. This page spells out exactly what gets erased, what to back up before you begin, and what 'going back to Windows' actually involves.
The installer takes the entire disk, not just the Windows partition. Anything you want to keep must live somewhere else before you start.
Read the installer's warning screen literally. ChromeOS Flex does not install 'alongside' Windows and does not respect your partitions. It claims the entire disk - the Windows partition, the data partition, the recovery partition, everything on that physical drive is wiped and replaced.
There is no dual boot option, no 'keep my files' choice, and no undo button afterwards. This is the single most important fact about Flex OS, and it is why the video's quick install deserves a slow pause before this step.
Before you install, move everything you care about to an external drive or a cloud account - somewhere that is not the disk being erased:
Then open the backup and check a few files are really there. A backup you have never opened is a hope, not a backup.
Still unsure? Do not install at all yet. Boot the USB and use Try it first - Flex OS runs entirely from the stick and your Windows disk is untouched. Live with it for an evening of real browsing. Only when you are sure this machine's future is browser-based should the erase become acceptable.
Yes, but only the long way. Going back means a complete fresh Windows installation from Microsoft's installation media, reinstalling your programs, and copying your files back from the backup. Your old Windows setup - its settings, programs and exact state - cannot be restored, because it no longer exists. Keep the Windows licence details of the PC noted down before you erase, in case you ever need them.
If the PC holds the only copy of family photos, business records or any data you have not backed up, stop here. Also stop if other people depend on Windows programs installed on that machine. Flex OS will still be free next week; erased data does not come back next week.
The full Flex OS 2025 download and installation process - bootable USB creation, installation and first setup, shown live step by step.
▶️ Watch Full VideoNo. The ChromeOS Flex installer takes the whole physical disk. All partitions on that disk - including a separate data partition - are erased during installation.
No. Try it first runs ChromeOS Flex entirely from the USB stick and does not install anything or erase your disk. It is the safe way to test the system and your hardware before deciding.
Realistically, no. The installation overwrites the disk structure, and data recovery after a full OS install is unreliable to the point of being a lottery ticket. This is exactly why the backup step has to happen before installation, not after.