Right click on the plugin (.plug file) -> open with -> choose program -> browse to notepad++ or enter/browse to "C:\WINDOWS\notepad.exe" check the box that says "Always use the selected program for this kind of file"
Stealthbot.net scripters recommend using notepad++ for anyone who's interested in learning more about scripting.
Notepad++ can be downloaded here: http://notepad-plus.sourceforge.net
notepad++ is awesome, highly recommended. Once you open it, be sure to go to settings > style configurator. Scroll down the languages and select VB / VBS. Type plug into the user ext box and click save and close. This will give you the proper syntax highlighting whenever you open a plugin
Also, go to Settings > Preferences, Edit Components tab. Where it says Tab Setting, make the tab size 3 and check the box "Replace by space". That way your indenting will look much cleaner when you post on here.
You can make the tab size whatever you want- it's your preference. - Most scripts here do use 3 space-indenting. (Indenting guide)