Carbide.ui Series 40 Theme Edition can create themes only for Symbian and Series 40 devices. Since Nokia C5-03 runs Symbian, you can use the utility to create one for your phone. Launch the software, click the Create a new Theme option, type a name, choose a template, select your device from the list, press Finish and after that follow the on-screen instructions to select your theme options and features. If you have issues, you can access the user guide from the Help menu. Also, you can use the video tutorial from the review page of the product.