There are several times when you may have made modifications and customized a theme you are using on Windows XP or Windows Vista, in such cases if you apply a new theme, all your modifications will be lost, so it is better to always keep a backup of the theme you modified, so that you can apply them again without having to modify the settings once again.
Here are some simple steps that will help you backup your themes in Windows XP and Vista, except for the first step, all the other steps are similar in both Windows XP and Vista.
Step 1: The steps are slightly different for Windows XP and Vista, please follow the instructions according to the operating system you are using.
For Windows XP Users: Right click on your desktop and select Properties and navigate to the Themes Tab or Appearance tab for style.
For Windows Vista Users: Right click on the desktop and click on the Personalize link in the menu, from the available options click on the Themes link.
Step 2: In the new window that opens up (see screenshot below), your current theme will be selected by default, click on the Save As button.
Note: The themes screen will have more tabs in Windows XP.
Step 3: In the file save dialog that appears give your theme a name and save it to a safe location. Once you have saved the file a .theme file will be created where all your settings will be saved.
Bonus Step Restoring Themes: If you want to restore your desktop to use a theme you have saved earlier, you can do that by expanding the themes select box and choosing the name of the theme you saved. If the theme is not available in the list, you can click on the browse button and open the theme from the location you saved in step 3.