Try one of these methods:
1: Recommended: In Windows, go to Control Panel, Click Programs and Features, look for Remix OS in the list, then follow the prompt to uninstall it.
2: In Windows File Explorer, go to your hard drive (C:), find the folder RemixOS, look in the list for the Uninstall Remix OS app. All Remix OS components will be ununstalled except the data image and the Uninstall app. You can delete both yourself.
3: Not recommended: In Windows File Explorer, go to your hard drive (C:), find the folder RemixOS, select the items you want to delete. (This option will not delete all Remix OS components. Some items, including the GRUB menu may still exist.)