Hello guys I've been wondering...how can I change an icon to an .exe ?

For example in the dir C:\Windows there are several exe's that have horrible icons, for example the "Writer.exe" in that directory.
If I open it with Resource Hacker, I'm able to change the icon, but when I try to save changes it says that I can't...blah blah...
For me it was impossible to take ownership of the .exe file, but who knows... maybe I was doing something wrong, or that's not the proper way to treat with an .exe file

Salutes