Why cannot I create a new project with path to desktop?

I can only create a new project with the default path “C:\Users\Hanlun\Documents\New Unity Project”. Whenever I set the path to others, like to the desktop “C:\Users\Hanlun\Desktop”, the “create” button becomes grey(unclickable), thus I cannot create a project. Why?

The folder you select has to be empty.
You should create a new folder on the desktop, and create your project in that folder.