is there a way to set Windows 7 to globally use UTF-8 as standard?
its really annoying to set every single text editor to use it.
The short answer is no, it is not possible.
To elaborate, I am afraid you won't find a global encoding option in Windows 7 that lets you both 1) set a global default which 2) all the application you listed would obey.
Also, I would also like to ask that what is the problem here that you are trying to solve?
It is up to application to choose whether they use unicode internally to represent data. While use of unicode is encouraged, you may never be sure that all your applications in fact do internally support it.
What you can do, however is to change the default character encoding for each of the listed applications:
It's not possible mainly because Windows does not allow UTF-8 as the system ANSI codepage even though it does have an ANSI codepage for UTF-8, codepage 65001. There seem to be several reasons for this:
Microsoft's own Michael Kaplan has a blog, "Sorting it all Out", with several posts on related topics. He may even publish a post on topics you email him directly about.