Most people are not using anywhere near the entire amount of drive space on their Windows 10 C: volume. And it's so easy to shrink the C: volume while you are

Most people are not using anywhere near the entire amount of drive space on their Windows 10 C: volume. And it's so easy to shrink the C: volume while you are booted to W10, leaving over 64GB of unallocated space to format so you can do an additional clean install of W11 to the previously unused drive space, after booting to the W11 USB install media, without disturbing W10 in any way. The built-in Windows multi-boot menu accepts an additional entry for W11 alongside your present W10 boot entry, then the resulting dual boot menu will pop up every time you reboot so you have a choice of which partition to boot to, either W10 or W11. The most recently installed version of Windows will automatically become the default OS appearing on the bootmenu if you do not change which one you want to be default afterward. Whichever partition you choose to boot to will be autoenumerated as your C: volume at the time, with remaining "unhidden" volumes occupying other alphabetical designations. i.e. when you boot to W11 it will be your C: volume and your W10 partition will not be C: again until you reboot to W10. The built-in multiboot menu simply remains unseen when there is only a single boot entry, such as on a factory W10 PC. cons: -you basically update each OS separately -you back up each system separately -unless you make the desired adjustment to the OS's in a multiboot system, more than one correction for Daylight Savings Time may occur after that date arrives. Only the most frequently used OS should be the one to autoupdate the mainboard timeclock for DST Alternatively, without using the conventional Setup.exe to install W11 from the USB install media, you can place the W11 virgin fileset onto a formatted partition from an administrative command prompt using DISM.exe. i.e. in W10 after shrinking C: and formatting the unused space as new NTFS volume "T:", you plug in the W11 setup USB stick, cancel the setup/upgrade option then use W10 CMD line to access the files on the USB volume and bring in the W11 fileset to your target partition. Assuming your W11 USB drive is "U:" and your target NTFS volume is "T:", first use DISM to find out which versions of Windows 11 are available within the install.wim file: DISM.exe /get-imageinfo u:\sources\install.wim Most of the time the "pro" version of Windows will be the sixth choice, which is identified as Index 6. Apply W11 pro fileset to target volume "T:": DISM.exe /apply-image u:\sources\install.wim index:6 /applydir:t:\ -w11 can actually be applied to volumes smaller than 64GB this way also Without employing the consumer W11 Setup.exe routine, you would then need to manually add a W11 bootentry (pointing to your new Windows 11 fileset) into the existing (hidden) EFI folder that you have been using for W10 booting all along: bcdboot t:\windows This manual deployment approach can also be accomplished similarly from the CMD prompt when booted to the W11 install media itself, which can be helpful when your target partition is not empty, as Trusted Installer you will have fewer permission problems than a W10 Administrator.