If you mean TgaTool can`t find the paint program toi send the image to for editing then you will need to set this again manually
From the Prefs menu select "Select Editing Program" and then browse to the exe file of the paint program you want to use. If you can`t remember where the paint program is located then find the shortcut you normally use to run the paint program (on the start menu) and right-click on it and select properties. This will tell you where you need to browse to and even the exe filename