Is it safe to delete a large file in the C:$Extend$Deleted folder?

Remember that this directory is for files marked for deletion that are currently in use. If you've deleted a lot of stuff or uninstalled large applications recently, that could be why it’s taking up space. If a restart doesn’t solve it, you might need to look into some system tools to clean it up.

That folder is a special NTFS system location for files that are marked for deletion but are still being held open by an application. Usually, it gets cleared when the application releases the file. Have you tried rebooting your computer? Often that will fix the issue by freeing up any locked files.

Make sure you've emptied your recycle bin, but since you mentioned this isn't in there, it's likely because it’s in a special folder that you can't access normally. It might just be a temporary holding area. Rebooting your PC can help, as it might delete those files on its own once nothing is using them.