Question #1: are you using Vista, Windows 7 or Windows 8? Any of those operating systems, in agreement with just about every distribution of Linux and Apple OSs, believe that they have a duty to protect certain special files by requiring admin privileges.
Windows likes to protect system files, mostly in the /Windows directory and program files in either the /Program Files or /Program Files (x86) directories. Unless you are logged in as an administrator, you cannot change these files. Believe it or not, I agree with the situation and it's about time that Windows caught up.
Why in the world would I agree with limiting your use of your machine. YOUR MACHINE!!! Ahem.... I feel much better now. Well, it's because there are bad guys out there who do occasionally hack into machines. And there is bad malware (there's a saying: bad malware! As if there were good malware... you have to consider the source here.
) out there that love to hack into your machine. Without administrator access their potential damage is limited.
Same goes for you. You are by default a garden variety user without adminstrator privileges. So there are files you cannot edit.
But you can! Whatever program you are using to edit, all you have to do is use the start menu (assuming you're not being tortured by the despicable Windows 8. I don't even WANT to know how that one works....) to find the program, notepad for instance. Right click notepad and select "run as administrator" from the start menu there. Now you can edit your file.
Windows 8 claims you don't need a start menu! I suppose you could use Windows Explorer to do the same thing. I might start up the beast in my secure cage (Virtualbox) to check it out tonight.