A trick to open any file without .rar extension via WinRAR is to first double click on a .rar file then navigate to parent directory (double click on ..) and double click on a file you want to open. If the file is in the format readable by WinRAR, it will open it.
I did not know that WinRAR 5.01 will not corrupt iGO .zip file, I've been safely using 3.93 forever and it works perfectly every time.
Notepad++ works great for me.