Every file you have on your computer has an extension, for example picture files may have .jpg as an extensio or .bmp. An extension helps windows (or phones) in recognizing the file type so that the correct software can be used to open the file.
What windows does is that (by default) every file it has recognized it hides the extension.
What TUGzip does is create compressed files, it does not rename them. It will create files and one of the files it can create is .TAR, which you need to use when making themes.
Now when you have created a .TAR file you will need to rename its extension. To do so, if you are using XP, open any folder like go to my documents. Click tools on the top, click folder options. A window will open. In this window there will be three tabs on top. Click the second one labelled view. Scroll down, and you will come to an option saying "hide known file extension" . tHERE will be a box next to this option, uncheck it by clicking on it. Click OK. Now the files will be shown with the extension. Now go to the .TAR file you created. You will notice that along with the file .TAR is written. Rename the .TAR part to .THM. Now you have a working .THM file which you can use on ur phone.
In Vista, the method is the same but to access folder options, you must go to the control panel, there will be a folder option icon there, open it. and the rest is the same...




