How to disable Win key shortcut assignment?

I want to assign Win + U to a macro, but the Windows Utility Manager keeps overriding it. In other words, even though I assign that key combination to what I want through a macro program, using the key combo still launches the Utility Manager, and not the program that I want.

Is there a way to disable this, which appears to be a system default?

In fact, I'd like to be able to disable any default Win key combination. Is there a way to do this, and if so how?

Thanks.