In order to reset PhotoShop CS3 settings to default , do the following steps :
1.Hold down 3 Keys all together : Ctrl +Alt + Shift
2.Right click on photoshop icon on your desktop or in start menu and choose “Open”
3.When photoshop starts , you will get a dialog which asks you if you want to delete your current settings
4.Click on YES.
it is done 🙂