Remove Photoshop CS3 Beta before installing CS3.
Some early adopters are experiencing problems installing their new copy of Adobe CS3. If you tested the public beta version of Photoshop CS3 on your computer you will see the following cryptic error when you try to install the full version:
"Adobe Photoshop CS3 cannot be installed because it conflicts with: Adobe Photoshop CS3"
If you've seen this error, you must first remove the beta version of Photoshop CS3. That takes more than simply trashing the application folder.
Remove the Photoshop CS3 public beta on a Mac:
If you need to remove the Photoshop CS3 beta on a Mac, the easiest way is to use an uninstaller that is probably already tucked away in your Utilities folder (Applications/Utilities/Adobe Installers).
Chose the "Remove Adobe Photoshop CS3 Components" option and click next.
Remove the Photoshop CS3 public beta on Windows:
Windows XP: Uninstall via Add/Remove Programs in the Control Panel.
Windows Vista: Go to the Programs section of the Control Panel, select Uninstall a Program.
What if that doesn't work?
If the standard uninstall options do not solve your problem, or if you already trashed the Adobe Installers folder before running it, Adobe has created a special CS3Clean Script which will clean up the beta installation and allow you to install the shipping versions of Creative Suite 3:
Link: Adobe CS3Clean Script
Source: CreativeTechs officially recommends waiting until June before upgrading to Adobe CS3 — in fact we'll be running a tip on June 4th, 2007 titled "Can I upgrade to Adobe CS3 yet?" Until then we're adding an extra CS3 tip each week for those early adaptors who aren't content to listen to such conservative recommendations.