The trouble isn't XP nor any other fact, simply is unknowledge about of its use. For to delete .txt extensions (or any other hidden by OS), simply follow this instructions wrote below:
You have to delete the .txt ending at the end of the filename of each part. Just rename them and delete the .txt. If it isn't showing up, look up at the top of your screen. Click "Tools", then "Folder Options" Under "View", UNCHECK the box that says "Hide Extensions from Known File Types". You should then be able to see the .txt, rename the file and delete it (the .txt extension, of course).