WinToUSB can help you to convert a CD or DVD to ISO image file with a few simple steps.
Using WinToUSB to convert a CD or DVD to ISO image file:
- Insert the CD or DVD disc which you want to convert in your CD/DVD-ROM.
- Run WinToUSB as administrator.
- Click "Tools" > "CD/DVD To ISO".

- Select the CD/DVD drive in the drop-down list. If your CD/DVD drive is not correctly recognized by WinToUSB, you need to click the
button for the program to recognize the CD/DVD drive.
- Click the
button. A dialog window will appear asking you where you want to save the ISO file to, select where you want to save the ISO file and give it a name. 
- Click "OK". After clicking "OK", WinToUSB begins converting.

- Click "OK" when the conversion is complete. The CD or DVD disk has been converted to ISO image file now.

Follow these simple steps, you can convert a CD or DVD disc to ISO image file with WinToUSB easily.