When you boot from a USB stick to install Windows, the installer sees your computer as a collection of storage devices. It does not assume you want to destroy everything; it assumes you want a place to live.
When booting from your installation media (USB/DVD), choose the option. Look at the list of drives.
If you have a second internal hard drive, an SSD for games, or an external backup drive, the installer generally leaves these alone. Unless you manually select those partitions and click "Format" or "Delete" during the setup process, the data on them remains untouched. The Risks: When Other Drives Might Be Affected
The most common cause of accidental data loss is selecting the wrong drive during setup. In the installation menu, drives are often labeled generically as "Drive 0," "Drive 1," or "Drive 2," rather than by their volume names (like "Backup" or "Games"). If you have multiple drives of the exact same capacity, it is remarkably easy to accidentally select and format your secondary data drive. 2. Corrupting the Boot Record (MBR/GPT) does clean install wipe all drives exclusive
It is important to distinguish a "clean install" (using external media like a USB) from the "Reset this PC" feature found in Windows settings:
However, note that some partition layouts may have system-related partitions interspersed with data partitions. If you are uncertain about which partitions belong to the operating system, the safest approach is to back up your data and delete all partitions on the drive for a truly clean slate.
To guarantee that a clean install remains exclusive to your OS drive, follow these best practices: When you boot from a USB stick to
However, there is a critical difference: during the Reset This PC process, you may be presented with an option that asks whether you want to remove files from "Only the drive where Windows is installed" or "All drives." If you choose "All drives," the reset will erase data from every connected drive—not just the system drive. By default, resetting your PC only deletes files from the drive where Windows is installed, but you must pay close attention to avoid selecting the "All drives" option.
The most foolproof way to prevent accidental wiping or Windows placing boot files on the wrong drive is to unplug the data cables of secondary drives before starting the installation.
The partition you select will have all data, apps, and settings removed. If you install over an existing Windows partition without formatting it, your old files may be moved to a Windows.old folder rather than being deleted. Look at the list of drives
Settings, configurations, and personalization options from the device manufacturer. When Should You Perform a Clean Install?
A clean install does not automatically scan your PC and wipe every drive. It only modifies the specific drive/partition you tell it to modify. All other physical hard drives remain 100% intact.