Adobe Dreamweaver CS3 comes with an uninstaller on Mac OS. If you remove Dreamweaver CS3, use the uninstaller instead of manually deleting application folders by dragging them to the trash. Manually deleting folders before using the uninstaller can cause problems when you try to reinstall Dreamweaver CS3.
The uninstaller is designed to remove everything installed by Dreamweaver CS3.
Note: When you run the uninstaller, you are reminded to deactivate your software. If you plan to reinstall the Dreamweaver CS3 on the same machine, then considering keeping your activation.
Navigate to /Applications/Utilities/Adobe Installers and double-click the Add or Remove Adobe Dreamweaver CS3 alias. Follow the onscreen instructions to remove Dreamweaver CS3.
If you manually removed Dreamweaver CS3 by dragging it to the trash and are having problems reinstalling it, then run the Adobe CS5 Cleaner Tool.
Download the Adobe CS5 Cleaner Tool from http://www.adobe.com/support/contact/cs53clean.html and follow the instructions included with the script.