You save the theme on the Theme tab of the Display Properties dialog box (right-click the desktop, select Properties, and click the Theme tab). Click the Save As button; the Save As dialog box opens.
Locate the drive and folder you want to use to save your theme. Then type a filename for your theme in the File Name box and click Save to complete the process.
You are returned to the Theme tab, and your new theme appears in the Theme list. You can click OK to close the Display Properties dialog box.
You've created and saved a new theme!