Quoted from http://www.adobe.com/support/contact/cs4clean.html:
Adobe CS4 Clean Script
The Adobe CS4 Clean Script will help resolve installation problems experienced by users of Adobe Creative Suite 4 software. The script can clean up install records for any beta and pre-release installations of Adobe Creative Suite 4 or Point Products. The Adobe CS4 Clean Script is designed to not interfere with existing Creative Suite 3 products, but it allows you to specify if you wish to remove them as well.
- Back-up all data stored in Adobe product directories prior to using the CS4Clean Script, including custom plug-ins, preference files or profiles you have installed.
- Uninstall the Adobe Creative Suite 4 products prior to using the CS4 Clean Script.
- On Windows XP, uninstall via Add/Remove Programs in the Control Panel.
- On Windows Vista, in the Programs And Features section of the Control Panel, select Uninstall a Program.
- On Macintosh, the uninstaller is in Applications/Utilities/Adobe Installers.
- Download the appropriate file from below.
- Unzip the download, or mount the .dmg file (Mac). The download includes the script as well as a ReadMe file with detailed instructions.
- On Windows, right click CS4InstallerDatabaseUtility.exe and select Run As Administrator.
Note: When the Run As Administrator option is not available double click on CS4InstallerDatabaseUtility.exe.
- On Macintosh, double click Adobe Creative Suite Cleanup.
- Follow the on-screen prompt to complete the script. Once the script completes press Enter or Quit (Mac) to exit.
- Restart your system.
- Now you can proceed with your installation of the shipping version of Creative Suite 4.
It is important you read and carefully follow the ReadMe instructions included with the download.