Copyright issues

[Anas R.]

Hi all,

Couple of days ago I've released a modified version of the last GPLd version of 
Notepad2 
which was in 2004.
My modifications were:
- The installation and the shell integration
- Refining and formatting the web documentation and associating it with the 
application.
- Replacing graphic items (icons/toolbars)
- Some little modifications in the executable program itself. 
I've called My work "Notepad3", and I've wrote the following in the "About" 
dialog:

-----------
 Notepad3 1.0
(c) [myname] [year]
[myEmailAddress]
[myWebsite]

Notepad2 1.0.12
(c) Florian Balmar [year]
[hisEmailAddress]
[hisWebsite]

GPL 2.0 Notice
-----------

My question is: Am I broking GPL 2.0? Do I do anything wrong ligally or 
ethically? 

This question will lead to several questions:

What's software?
Code/compiled code?
or
Code + Documentation + Installation

If the first:
Do little modifications made for specific software deserves a copyright notice?
If the second:
Does the (About) dialog represent the executable program or the product as a 
whole: executable + documentation + installation


Best regards, 
  
-       Anas R.