I've finally found a way that works for me, and hasn't given me any problems or headaches with trying to change something to have the .lwtp file extention.... if you're still having problems after following CyberStalker's instructions, no matter what you do - as I was, I had actually completely given up on trying to create a theme for a while... then I got a thought (which is rare for me! lol) and tried something different... I went into the themes folder for limewire and copied one of the .lwtp files to where I had been working on my theme (-copied- NOT moved, incase anyone tries duplicating what I did), renamed it to have the same name as the theme I was working on (leaving the file extention as .lwtp) and then moved the renamed file and the folder for my theme to the limewire themes folder.... lo and behold, it worked!! And without the headache of extention-changes!!

Good luck to anyone working on making themes, and no matter how you do it I hope everything works out for you!!