This link has an alternative method of opening a file using the start
menu on the Task Bar
then browse to the file in the Run..
box then Select the program (Notepad) from a list
http://community.apachefriends.org/f/viewtopi ... 976#112976
Also you have to select to always use this program to open php files.
Same as right clicking on the php file and selecting to open it by using Notepad and follow the prompt windows.
If you are on Vista you may have to right click on the file and select to open it as an administrator.
I have never had any issues by simply dragging a file of unknown content into my text editor then just clicking on Save from the File menu to have it saved using it's original extension.
This is very much basic Windows file manipulation techniques and should be in the Windows Help files.
Until you master this technique you will have more problems down the track trying to edit non standard files in XAMPP like the conf and ini files etc.