When you are making a bootable USB stick using the Windows 7 USB DVD Download tool, it erases all data from your USB drive by formatting it. However, your USB flash drive may include some important data or may already be properly formatted. In this case, you may want to avoid formatting of your USB stick, but Windows 7 DVD tool does not have the appropriate option in its UI. In such a case, you can use a secret hidden registry tweak which will prevent Windows 7 DVD tool from formatting the USB drive.